Skip to content

Latest commit

 

History

History
2793 lines (2142 loc) · 94.6 KB

routing.rst

File metadata and controls

2793 lines (2142 loc) · 94.6 KB
.. index::
   single: Routing

Routing

When your application receives a request, it calls a :doc:`controller action </controller>` to generate the response. The routing configuration defines which action to run for each incoming URL. It also provides other useful features, like generating SEO-friendly URLs (e.g. /read/intro-to-symfony instead of index.php?article_id=57).

Creating Routes

Routes can be configured in YAML, XML, PHP or using either attributes or annotations. All formats provide the same features and performance, so choose your favorite. :ref:`Symfony recommends attributes <best-practice-controller-annotations>` because it's convenient to put the route and controller in the same place.

Creating Routes as Attributes or Annotations

On PHP 8, you can use native attributes to configure routes right away. On PHP 7, where attributes are not available, you can use annotations instead, provided by the Doctrine Annotations library.

In case you want to use annotations instead of attributes, run this command once in your application to enable them:

$ composer require doctrine/annotations
.. versionadded:: 5.2

    The ability to use PHP attributes to configure routes was introduced in
    Symfony 5.2. Prior to this, Doctrine Annotations were the only way to
    annotate controller actions with routing configuration.

This command also creates the following configuration file:

# config/routes/annotations.yaml
controllers:
    resource: '../../src/Controller/'
    type: annotation

kernel:
    resource: ../../src/Kernel.php
    type: annotation

This configuration tells Symfony to look for routes defined as annotations in any PHP class stored in the src/Controller/ directory.

Suppose you want to define a route for the /blog URL in your application. To do so, create a :doc:`controller class </controller>` like the following:

.. configuration-block::

    .. code-block:: php-annotations

        // src/Controller/BlogController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\Routing\Annotation\Route;

        class BlogController extends AbstractController
        {
            /**
             * @Route("/blog", name="blog_list")
             */
            public function list()
            {
                // ...
            }
        }

    .. code-block:: php-attributes

        // src/Controller/BlogController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\Routing\Annotation\Route;

        class BlogController extends AbstractController
        {
            #[Route('/blog', name: 'blog_list')]
            public function list()
            {
                // ...
            }
        }

This configuration defines a route called blog_list that matches when the user requests the /blog URL. When the match occurs, the application runs the list() method of the BlogController class.

Note

The query string of a URL is not considered when matching routes. In this example, URLs like /blog?foo=bar and /blog?foo=bar&bar=foo will also match the blog_list route.

Caution!

If you define multiple PHP classes in the same file, Symfony only loads the routes of the first class, ignoring all the other routes.

The route name (blog_list) is not important for now, but it will be essential later when :ref:`generating URLs <routing-generating-urls>`. You only have to keep in mind that each route name must be unique in the application.

Creating Routes in YAML, XML or PHP Files

Instead of defining routes in the controller classes, you can define them in a separate YAML, XML or PHP file. The main advantage is that they don't require any extra dependency. The main drawback is that you have to work with multiple files when checking the routing of some controller action.

The following example shows how to define in YAML/XML/PHP a route called blog_list that associates the /blog URL with the list() action of the BlogController:

.. configuration-block::

    .. code-block:: yaml

        # config/routes.yaml
        blog_list:
            path: /blog
            # the controller value has the format 'controller_class::method_name'
            controller: App\Controller\BlogController::list

            # if the action is implemented as the __invoke() method of the
            # controller class, you can skip the '::method_name' part:
            # controller: App\Controller\BlogController

    .. code-block:: xml

        <!-- config/routes.xml -->
        <?xml version="1.0" encoding="UTF-8" ?>
        <routes xmlns="http://symfony.com/schema/routing"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/routing
                https://symfony.com/schema/routing/routing-1.0.xsd">

            <!-- the controller value has the format 'controller_class::method_name' -->
            <route id="blog_list" path="/blog"
                   controller="App\Controller\BlogController::list"/>

            <!-- if the action is implemented as the __invoke() method of the
                 controller class, you can skip the '::method_name' part:
                 controller="App\Controller\BlogController"/> -->
        </routes>

    .. code-block:: php

        // config/routes.php
        use App\Controller\BlogController;
        use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;

        return function (RoutingConfigurator $routes) {
            $routes->add('blog_list', '/blog')
                // the controller value has the format [controller_class, method_name]
                ->controller([BlogController::class, 'list'])

                // if the action is implemented as the __invoke() method of the
                // controller class, you can skip the 'method_name' part:
                // ->controller(BlogController::class)
            ;
        };

Matching HTTP Methods

By default, routes match any HTTP verb (GET, POST, PUT, etc.) Use the methods option to restrict the verbs each route should respond to:

.. configuration-block::

    .. code-block:: php-annotations

        // src/Controller/BlogApiController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\HttpFoundation\Response;
        use Symfony\Component\Routing\Annotation\Route;

        class BlogApiController extends AbstractController
        {
            /**
             * @Route("/api/posts/{id}", methods={"GET","HEAD"})
             */
            public function show(int $id): Response
            {
                // ... return a JSON response with the post
            }

            /**
             * @Route("/api/posts/{id}", methods={"PUT"})
             */
            public function edit(int $id): Response
            {
                // ... edit a post
            }
        }

    .. code-block:: php-attributes

        // src/Controller/BlogApiController.php
        namespace App\Controller;

        // ...

        class BlogApiController extends AbstractController
        {
            #[Route('/api/posts/{id}', methods: ['GET', 'HEAD'])]
            public function show(int $id)
            {
                // ... return a JSON response with the post
            }

            #[Route('/api/posts/{id}', methods: ['PUT'])]
            public function edit(int $id)
            {
                // ... edit a post
            }
        }

    .. code-block:: yaml

        # config/routes.yaml
        api_post_show:
            path:       /api/posts/{id}
            controller: App\Controller\BlogApiController::show
            methods:    GET|HEAD

        api_post_edit:
            path:       /api/posts/{id}
            controller: App\Controller\BlogApiController::edit
            methods:    PUT

    .. code-block:: xml

        <!-- config/routes.xml -->
        <?xml version="1.0" encoding="UTF-8" ?>
        <routes xmlns="http://symfony.com/schema/routing"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/routing
                https://symfony.com/schema/routing/routing-1.0.xsd">

            <route id="api_post_show" path="/api/posts/{id}"
                controller="App\Controller\BlogApiController::show"
                methods="GET|HEAD"/>

            <route id="api_post_edit" path="/api/posts/{id}"
                controller="App\Controller\BlogApiController::edit"
                methods="PUT"/>
        </routes>

    .. code-block:: php

        // config/routes.php
        use App\Controller\BlogApiController;
        use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;

        return function (RoutingConfigurator $routes) {
            $routes->add('api_post_show', '/api/posts/{id}')
                ->controller([BlogApiController::class, 'show'])
                ->methods(['GET', 'HEAD'])
            ;
            $routes->add('api_post_edit', '/api/posts/{id}')
                ->controller([BlogApiController::class, 'edit'])
                ->methods(['PUT'])
            ;
        };

Tip

HTML forms only support GET and POST methods. If you're calling a route with a different method from an HTML form, add a hidden field called _method with the method to use (e.g. <input type="hidden" name="_method" value="PUT"/>). If you create your forms with :doc:`Symfony Forms </forms>` this is done automatically for you.

Matching Expressions

Use the condition option if you need some route to match based on some arbitrary matching logic:

.. configuration-block::

    .. code-block:: php-annotations

        // src/Controller/DefaultController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\HttpFoundation\Response;
        use Symfony\Component\Routing\Annotation\Route;

        class DefaultController extends AbstractController
        {
            /**
             * @Route(
             *     "/contact",
             *     name="contact",
             *     condition="context.getMethod() in ['GET', 'HEAD'] and request.headers.get('User-Agent') matches '/firefox/i'"
             * )
             *
             * expressions can also include config parameters:
             * condition: "request.headers.get('User-Agent') matches '%app.allowed_browsers%'"
             */
            public function contact(): Response
            {
                // ...
            }
        }

    .. code-block:: php-attributes

        // src/Controller/DefaultController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\Routing\Annotation\Route;

        class DefaultController extends AbstractController
        {
            #[Route(
                '/contact',
                name: 'contact',
                condition: "context.getMethod() in ['GET', 'HEAD'] and request.headers.get('User-Agent') matches '/firefox/i'",
            )]
            // expressions can also include config parameters:
            // condition: "request.headers.get('User-Agent') matches '%app.allowed_browsers%'"
            public function contact()
            {
                // ...
            }
        }

    .. code-block:: yaml

        # config/routes.yaml
        contact:
            path:       /contact
            controller: 'App\Controller\DefaultController::contact'
            condition:  "context.getMethod() in ['GET', 'HEAD'] and request.headers.get('User-Agent') matches '/firefox/i'"
            # expressions can also include config parameters:
            # condition: "request.headers.get('User-Agent') matches '%app.allowed_browsers%'"

    .. code-block:: xml

        <!-- config/routes.xml -->
        <?xml version="1.0" encoding="UTF-8" ?>
        <routes xmlns="http://symfony.com/schema/routing"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/routing
                https://symfony.com/schema/routing/routing-1.0.xsd">

            <route id="contact" path="/contact" controller="App\Controller\DefaultController::contact">
                <condition>context.getMethod() in ['GET', 'HEAD'] and request.headers.get('User-Agent') matches '/firefox/i'</condition>
                <!-- expressions can also include config parameters: -->
                <!-- <condition>request.headers.get('User-Agent') matches '%app.allowed_browsers%'</condition> -->
            </route>
        </routes>

    .. code-block:: php

        // config/routes.php
        use App\Controller\DefaultController;
        use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;

        return function (RoutingConfigurator $routes) {
            $routes->add('contact', '/contact')
                ->controller([DefaultController::class, 'contact'])
                ->condition('context.getMethod() in ["GET", "HEAD"] and request.headers.get("User-Agent") matches "/firefox/i"')
                // expressions can also include config parameters:
                // 'request.headers.get("User-Agent") matches "%app.allowed_browsers%"'
            ;
        };

The value of the condition option is any valid :doc:`ExpressionLanguage expression </components/expression_language/syntax>` and can use any of these variables created by Symfony:

context
An instance of :class:`Symfony\\Component\\Routing\\RequestContext`, which holds the most fundamental information about the route being matched.
request
The :ref:`Symfony Request <component-http-foundation-request>` object that represents the current request.

Behind the scenes, expressions are compiled down to raw PHP. Because of this, using the condition key causes no extra overhead beyond the time it takes for the underlying PHP to execute.

Caution!

Conditions are not taken into account when generating URLs (which is explained later in this article).

Debugging Routes

As your application grows, you'll eventually have a lot of routes. Symfony includes some commands to help you debug routing issues. First, the debug:router command lists all your application routes in the same order in which Symfony evaluates them:

$ php bin/console debug:router

----------------  -------  -------  -----  --------------------------------------------
Name              Method   Scheme   Host   Path
----------------  -------  -------  -----  --------------------------------------------
homepage          ANY      ANY      ANY    /
contact           GET      ANY      ANY    /contact
contact_process   POST     ANY      ANY    /contact
article_show      ANY      ANY      ANY    /articles/{_locale}/{year}/{title}.{_format}
blog              ANY      ANY      ANY    /blog/{page}
blog_show         ANY      ANY      ANY    /blog/{slug}
----------------  -------  -------  -----  --------------------------------------------

Pass the name (or part of the name) of some route to this argument to print the route details:

$ php bin/console debug:router app_lucky_number

+-------------+---------------------------------------------------------+
| Property    | Value                                                   |
+-------------+---------------------------------------------------------+
| Route Name  | app_lucky_number                                        |
| Path        | /lucky/number/{max}                                     |
| ...         | ...                                                     |
| Options     | compiler_class: Symfony\Component\Routing\RouteCompiler |
|             | utf8: true                                              |
+-------------+---------------------------------------------------------+

The other command is called router:match and it shows which route will match the given URL. It's useful to find out why some URL is not executing the controller action that you expect:

$ php bin/console router:match /lucky/number/8

  [OK] Route "app_lucky_number" matches

Route Parameters

The previous examples defined routes where the URL never changes (e.g. /blog). However, it's common to define routes where some parts are variable. For example, the URL to display some blog post will probably include the title or slug (e.g. /blog/my-first-post or /blog/all-about-symfony).

In Symfony routes, variable parts are wrapped in { ... } and they must have a unique name. For example, the route to display the blog post contents is defined as /blog/{slug}:

.. configuration-block::

    .. code-block:: php-annotations

        // src/Controller/BlogController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\HttpFoundation\Response;
        use Symfony\Component\Routing\Annotation\Route;

        class BlogController extends AbstractController
        {
            // ...

            /**
             * @Route("/blog/{slug}", name="blog_show")
             */
            public function show(string $slug): Response
            {
                // $slug will equal the dynamic part of the URL
                // e.g. at /blog/yay-routing, then $slug='yay-routing'

                // ...
            }
        }

    .. code-block:: php-attributes

        // src/Controller/BlogController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\Routing\Annotation\Route;

        class BlogController extends AbstractController
        {
            // ...

            #[Route('/blog/{slug}', name: 'blog_show')]
            public function show(string $slug)
            {
                // $slug will equal the dynamic part of the URL
                // e.g. at /blog/yay-routing, then $slug='yay-routing'

                // ...
            }
        }

    .. code-block:: yaml

        # config/routes.yaml
        blog_show:
            path:       /blog/{slug}
            controller: App\Controller\BlogController::show

    .. code-block:: xml

        <!-- config/routes.xml -->
        <?xml version="1.0" encoding="UTF-8" ?>
        <routes xmlns="http://symfony.com/schema/routing"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/routing
                https://symfony.com/schema/routing/routing-1.0.xsd">

            <route id="blog_show" path="/blog/{slug}"
                   controller="App\Controller\BlogController::show"/>
        </routes>

    .. code-block:: php

        // config/routes.php
        use App\Controller\BlogController;
        use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;

        return function (RoutingConfigurator $routes) {
            $routes->add('blog_show', '/blog/{slug}')
                ->controller([BlogController::class, 'show'])
            ;
        };

The name of the variable part ({slug} in this example) is used to create a PHP variable where that route content is stored and passed to the controller. If a user visits the /blog/my-first-post URL, Symfony executes the show() method in the BlogController class and passes a $slug = 'my-first-post' argument to the show() method.

Routes can define any number of parameters, but each of them can only be used once on each route (e.g. /blog/posts-about-{category}/page/{pageNumber}).

Parameters Validation

Imagine that your application has a blog_show route (URL: /blog/{slug}) and a blog_list route (URL: /blog/{page}). Given that route parameters accept any value, there's no way to differentiate both routes.

If the user requests /blog/my-first-post, both routes will match and Symfony will use the route which was defined first. To fix this, add some validation to the {page} parameter using the requirements option:

.. configuration-block::

    .. code-block:: php-annotations

        // src/Controller/BlogController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\HttpFoundation\Response;
        use Symfony\Component\Routing\Annotation\Route;

        class BlogController extends AbstractController
        {
            /**
             * @Route("/blog/{page}", name="blog_list", requirements={"page"="\d+"})
             */
            public function list(int $page): Response
            {
                // ...
            }

            /**
             * @Route("/blog/{slug}", name="blog_show")
             */
            public function show(string $slug): Response
            {
                // ...
            }
        }

    .. code-block:: php-attributes

        // src/Controller/BlogController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\Routing\Annotation\Route;

        class BlogController extends AbstractController
        {
            #[Route('/blog/{page}', name: 'blog_list', requirements: ['page' => '\d+'])]
            public function list(int $page)
            {
                // ...
            }

            #[Route('/blog/{slug}', name: 'blog_show')]
            public function show($slug)
            {
                // ...
            }
        }

    .. code-block:: yaml

        # config/routes.yaml
        blog_list:
            path:       /blog/{page}
            controller: App\Controller\BlogController::list
            requirements:
                page: '\d+'

        blog_show:
            path:       /blog/{slug}
            controller: App\Controller\BlogController::show

    .. code-block:: xml

        <!-- config/routes.xml -->
        <?xml version="1.0" encoding="UTF-8" ?>
        <routes xmlns="http://symfony.com/schema/routing"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/routing
                https://symfony.com/schema/routing/routing-1.0.xsd">

            <route id="blog_list" path="/blog/{page}" controller="App\Controller\BlogController::list">
                <requirement key="page">\d+</requirement>
            </route>

            <route id="blog_show" path="/blog/{slug}"
                   controller="App\Controller\BlogController::show"/>
        </routes>

    .. code-block:: php

        // config/routes.php
        use App\Controller\BlogController;
        use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;

        return function (RoutingConfigurator $routes) {
            $routes->add('blog_list', '/blog/{page}')
                ->controller([BlogController::class, 'list'])
                ->requirements(['page' => '\d+'])
            ;

            $routes->add('blog_show', '/blog/{slug}')
                ->controller([BlogController::class, 'show'])
            ;
            // ...
        };

The requirements option defines the PHP regular expressions that route parameters must match for the entire route to match. In this example, \d+ is a regular expression that matches a digit of any length. Now:

URL Route Parameters
/blog/2 blog_list $page = 2
/blog/my-first-post blog_show $slug = my-first-post

Tip

Route requirements (and route paths too) can include :ref:`container parameters <configuration-parameters>`, which is useful to define complex regular expressions once and reuse them in multiple routes.

Tip

Parameters also support PCRE Unicode properties, which are escape sequences that match generic character types. For example, \p{Lu} matches any uppercase character in any language, \p{Greek} matches any Greek character, etc.

Note

When using regular expressions in route parameters, you can set the utf8 route option to true to make any . character match any UTF-8 characters instead of just a single byte.

If you prefer, requirements can be inlined in each parameter using the syntax {parameter_name<requirements>}. This feature makes configuration more concise, but it can decrease route readability when requirements are complex:

.. configuration-block::

    .. code-block:: php-annotations

        // src/Controller/BlogController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\HttpFoundation\Response;
        use Symfony\Component\Routing\Annotation\Route;

        class BlogController extends AbstractController
        {
            /**
             * @Route("/blog/{page<\d+>}", name="blog_list")
             */
            public function list(int $page): Response
            {
                // ...
            }
        }

    .. code-block:: php-attributes

        // src/Controller/BlogController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\Routing\Annotation\Route;

        class BlogController extends AbstractController
        {
            #[Route('/blog/{page<\d+>}', name: 'blog_list')]
            public function list(int $page)
            {
                // ...
            }
        }

    .. code-block:: yaml

        # config/routes.yaml
        blog_list:
            path:       /blog/{page<\d+>}
            controller: App\Controller\BlogController::list

    .. code-block:: xml

        <!-- config/routes.xml -->
        <?xml version="1.0" encoding="UTF-8" ?>
        <routes xmlns="http://symfony.com/schema/routing"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/routing
                https://symfony.com/schema/routing/routing-1.0.xsd">

            <route id="blog_list" path="/blog/{page<\d+>}"
                   controller="App\Controller\BlogController::list"/>

            <!-- ... -->
        </routes>

    .. code-block:: php

        // config/routes.php
        use App\Controller\BlogController;
        use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;

        return function (RoutingConfigurator $routes) {
            $routes->add('blog_list', '/blog/{page<\d+>}')
                ->controller([BlogController::class, 'list'])
            ;
            // ...
        };

Optional Parameters

In the previous example, the URL of blog_list is /blog/{page}. If users visit /blog/1, it will match. But if they visit /blog, it will not match. As soon as you add a parameter to a route, it must have a value.

You can make blog_list once again match when the user visits /blog by adding a default value for the {page} parameter. When using annotations, default values are defined in the arguments of the controller action. In the other configuration formats they are defined with the defaults option:

.. configuration-block::

    .. code-block:: php-annotations

        // src/Controller/BlogController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\HttpFoundation\Response;
        use Symfony\Component\Routing\Annotation\Route;

        class BlogController extends AbstractController
        {
            /**
             * @Route("/blog/{page}", name="blog_list", requirements={"page"="\d+"})
             */
            public function list(int $page = 1): Response
            {
                // ...
            }
        }

    .. code-block:: php-attributes

        // src/Controller/BlogController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\Routing\Annotation\Route;

        class BlogController extends AbstractController
        {
            #[Route('/blog/{page}', name: 'blog_list', requirements: ['page' => '\d+'])]
            public function list(int $page = 1)
            {
                // ...
            }
        }

    .. code-block:: yaml

        # config/routes.yaml
        blog_list:
            path:       /blog/{page}
            controller: App\Controller\BlogController::list
            defaults:
                page: 1
            requirements:
                page: '\d+'

        blog_show:
            # ...

    .. code-block:: xml

        <!-- config/routes.xml -->
        <?xml version="1.0" encoding="UTF-8" ?>
        <routes xmlns="http://symfony.com/schema/routing"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/routing
                https://symfony.com/schema/routing/routing-1.0.xsd">

            <route id="blog_list" path="/blog/{page}" controller="App\Controller\BlogController::list">
                <default key="page">1</default>

                <requirement key="page">\d+</requirement>
            </route>

            <!-- ... -->
        </routes>

    .. code-block:: php

        // config/routes.php
        use App\Controller\BlogController;
        use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;

        return function (RoutingConfigurator $routes) {
            $routes->add('blog_list', '/blog/{page}')
                ->controller([BlogController::class, 'list'])
                ->defaults(['page' => 1])
                ->requirements(['page' => '\d+'])
            ;
        };

Now, when the user visits /blog, the blog_list route will match and $page will default to a value of 1.

Caution!

You can have more than one optional parameter (e.g. /blog/{slug}/{page}), but everything after an optional parameter must be optional. For example, /{page}/blog is a valid path, but page will always be required (i.e. /blog will not match this route).

If you want to always include some default value in the generated URL (for example to force the generation of /blog/1 instead of /blog in the previous example) add the ! character before the parameter name: /blog/{!page}

As it happens with requirements, default values can also be inlined in each parameter using the syntax {parameter_name?default_value}. This feature is compatible with inlined requirements, so you can inline both in a single parameter:

.. configuration-block::

    .. code-block:: php-annotations

        // src/Controller/BlogController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\HttpFoundation\Response;
        use Symfony\Component\Routing\Annotation\Route;

        class BlogController extends AbstractController
        {
            /**
             * @Route("/blog/{page<\d+>?1}", name="blog_list")
             */
            public function list(int $page): Response
            {
                // ...
            }
        }

    .. code-block:: php-attributes

        // src/Controller/BlogController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\Routing\Annotation\Route;

        class BlogController extends AbstractController
        {
            #[Route('/blog/{page<\d+>?1}', name: 'blog_list')]
            public function list(int $page)
            {
                // ...
            }
        }

    .. code-block:: yaml

        # config/routes.yaml
        blog_list:
            path:       /blog/{page<\d+>?1}
            controller: App\Controller\BlogController::list

    .. code-block:: xml

        <!-- config/routes.xml -->
        <?xml version="1.0" encoding="UTF-8" ?>
        <routes xmlns="http://symfony.com/schema/routing"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/routing
                https://symfony.com/schema/routing/routing-1.0.xsd">

            <route id="blog_list" path="/blog/{page<\d+>?1}"
                   controller="App\Controller\BlogController::list"/>

            <!-- ... -->
        </routes>

    .. code-block:: php

        // config/routes.php
        use App\Controller\BlogController;
        use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;

        return function (RoutingConfigurator $routes) {
            $routes->add('blog_list', '/blog/{page<\d+>?1}')
                ->controller([BlogController::class, 'list'])
            ;
        };

Tip

To give a null default value to any parameter, add nothing after the ? character (e.g. /blog/{page?}).

Priority Parameter

.. versionadded:: 5.1

    The ``priority`` parameter was introduced in Symfony 5.1

When defining a greedy pattern that matches many routes, this may be at the beginning of your routing collection and prevents any route defined after to be matched. A priority optional parameter is available in order to let you choose the order of your routes, and it is only available when using annotations.

.. configuration-block::

    .. code-block:: php-annotations

        // src/Controller/BlogController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\Routing\Annotation\Route;

        class BlogController extends AbstractController
        {
            /**
             * This route has a greedy pattern and is defined first.
             *
             * @Route("/blog/{slug}", name="blog_show")
             */
            public function show(string $slug)
            {
                // ...
            }

            /**
             * This route could not be matched without defining a higher priority than 0.
             *
             * @Route("/blog/list", name="blog_list", priority=2)
             */
            public function list()
            {
                // ...
            }
        }

    .. code-block:: php-attributes

        // src/Controller/BlogController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\Routing\Annotation\Route;

        class BlogController extends AbstractController
        {
            /**
             * This route has a greedy pattern and is defined first.
             */
            #[Route('/blog/{slug}', name: 'blog_show')]
            public function show(string $slug)
            {
                // ...
            }

            /**
             * This route could not be matched without defining a higher priority than 0.
             */
            #[Route('/blog/list', name: 'blog_list', priority: 2)]
            public function list()
            {
                // ...
            }
        }

The priority parameter expects an integer value. Routes with higher priority are sorted before routes with lower priority. The default value when it is not defined is 0.

Parameter Conversion

A common routing need is to convert the value stored in some parameter (e.g. an integer acting as the user ID) into another value (e.g. the object that represents the user). This feature is called "param converter" and is only available when using annotations to define routes.

To add support for "param converters" we need SensioFrameworkExtraBundle:

$ composer require sensio/framework-extra-bundle

Now, keep the previous route configuration, but change the arguments of the controller action. Instead of string $slug, add BlogPost $post:

// src/Controller/BlogController.php
namespace App\Controller;

use App\Entity\BlogPost;
use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\Routing\Annotation\Route;

class BlogController extends AbstractController
{
    // ...

    /**
     * @Route("/blog/{slug}", name="blog_show")
     */
    public function show(BlogPost $post): Response
    {
        // $post is the object whose slug matches the routing parameter

        // ...
    }
}

If your controller arguments include type-hints for objects (BlogPost in this case), the "param converter" makes a database request to find the object using the request parameters (slug in this case). If no object is found, Symfony generates a 404 response automatically.

Read the full param converter documentation to learn about the converters provided by Symfony and how to configure them.

Special Parameters

In addition to your own parameters, routes can include any of the following special parameters created by Symfony:

_controller
This parameter is used to determine which controller and action is executed when the route is matched.
_format
The matched value is used to set the "request format" of the Request object. This is used for such things as setting the Content-Type of the response (e.g. a json format translates into a Content-Type of application/json).
_fragment
Used to set the fragment identifier, which is the optional last part of a URL that starts with a # character and is used to identify a portion of a document.
_locale
Used to set the :ref:`locale <translation-locale-url>` on the request.

You can include these attributes (except _fragment) both in individual routes and in route imports. Symfony defines some special attributes with the same name (except for the leading underscore) so you can define them easier:

.. configuration-block::

    .. code-block:: php-annotations

        // src/Controller/ArticleController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\HttpFoundation\Response;
        use Symfony\Component\Routing\Annotation\Route;

        class ArticleController extends AbstractController
        {
            /**
             * @Route(
             *     "/articles/{_locale}/search.{_format}",
             *     locale="en",
             *     format="html",
             *     requirements={
             *         "_locale": "en|fr",
             *         "_format": "html|xml",
             *     }
             * )
             */
            public function search(): Response
            {
            }
        }

    .. code-block:: php-attributes

        // src/Controller/ArticleController.php
        namespace App\Controller;

        // ...
        class ArticleController extends AbstractController
        {
            #[Route(
                path: '/articles/{_locale}/search.{_format}',
                locale: 'en',
                format: 'html',
                requirements: [
                    '_locale' => 'en|fr',
                    '_format' => 'html|xml',
                ],
            )]
            public function search()
            {
            }
        }

    .. code-block:: yaml

        # config/routes.yaml
        article_search:
          path:        /articles/{_locale}/search.{_format}
          controller:  App\Controller\ArticleController::search
          locale:      en
          format:      html
          requirements:
              _locale: en|fr
              _format: html|xml

    .. code-block:: xml

        <!-- config/routes.xml -->
        <?xml version="1.0" encoding="UTF-8" ?>
        <routes xmlns="http://symfony.com/schema/routing"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/routing
                https://symfony.com/schema/routing/routing-1.0.xsd">

            <route id="article_search"
                path="/articles/{_locale}/search.{_format}"
                controller="App\Controller\ArticleController::search"
                locale="en"
                format="html">

                <requirement key="_locale">en|fr</requirement>
                <requirement key="_format">html|rss</requirement>

            </route>
        </routes>

    .. code-block:: php

        // config/routes.php
        namespace Symfony\Component\Routing\Loader\Configurator;

        use App\Controller\ArticleController;

        return function (RoutingConfigurator $routes) {
            $routes->add('article_show', '/articles/{_locale}/search.{_format}')
                ->controller([ArticleController::class, 'search'])
                ->locale('en')
                ->format('html')
                ->requirements([
                    '_locale' => 'en|fr',
                    '_format' => 'html|rss',
                ])
            ;
        };

Extra Parameters

In the defaults option of a route you can optionally define parameters not included in the route configuration. This is useful to pass extra arguments to the controllers of the routes:

.. configuration-block::

    .. code-block:: php-annotations

        // src/Controller/BlogController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\HttpFoundation\Response;
        use Symfony\Component\Routing\Annotation\Route;

        class BlogController extends AbstractController
        {
            /**
             * @Route("/blog/{page}", name="blog_index", defaults={"page": 1, "title": "Hello world!"})
             */
            public function index(int $page, string $title): Response
            {
                // ...
            }
        }

    .. code-block:: php-attributes

        // src/Controller/BlogController.php
        namespace App\Controller;

        use Symfony\Component\Routing\Annotation\Route;

        class BlogController
        {
            #[Route('/blog/{page}', name: 'blog_index', defaults: ['page' => 1, 'title' => 'Hello world!'])]
            public function index(int $page, string $title)
            {
                // ...
            }
        }

    .. code-block:: yaml

        # config/routes.yaml
        blog_index:
            path:       /blog/{page}
            controller: App\Controller\BlogController::index
            defaults:
                page: 1
                title: "Hello world!"

    .. code-block:: xml

        <!-- config/routes.xml -->
        <?xml version="1.0" encoding="UTF-8" ?>
        <routes xmlns="http://symfony.com/schema/routing"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/routing
                https://symfony.com/schema/routing/routing-1.0.xsd">

            <route id="blog_index" path="/blog/{page}" controller="App\Controller\BlogController::index">
                <default key="page">1</default>
                <default key="title">Hello world!</default>
            </route>
        </routes>

    .. code-block:: php

        // config/routes.php
        use App\Controller\BlogController;
        use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;

        return function (RoutingConfigurator $routes) {
            $routes->add('blog_index', '/blog/{page}')
                ->controller([BlogController::class, 'index'])
                ->defaults([
                    'page'  => 1,
                    'title' => 'Hello world!',
                ])
            ;
        };

Slash Characters in Route Parameters

Route parameters can contain any values except the / slash character, because that's the character used to separate the different parts of the URLs. For example, if the token value in the /share/{token} route contains a / character, this route won't match.

A possible solution is to change the parameter requirements to be more permissive:

.. configuration-block::

    .. code-block:: php-annotations

        // src/Controller/DefaultController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\HttpFoundation\Response;
        use Symfony\Component\Routing\Annotation\Route;

        class DefaultController extends AbstractController
        {
            /**
             * @Route("/share/{token}", name="share", requirements={"token"=".+"})
             */
            public function share($token): Response
            {
                // ...
            }
        }

    .. code-block:: php-attributes

        // src/Controller/DefaultController.php
        namespace App\Controller;

        use Symfony\Component\Routing\Annotation\Route;

        class DefaultController
        {
            #[Route('/share/{token}', name: 'share', requirements: ['token' => '.+'])]
            public function share($token)
            {
                // ...
            }
        }

    .. code-block:: yaml

        # config/routes.yaml
        share:
            path:       /share/{token}
            controller: App\Controller\DefaultController::share
            requirements:
                token: .+

    .. code-block:: xml

        <!-- config/routes.xml -->
        <?xml version="1.0" encoding="UTF-8" ?>
        <routes xmlns="http://symfony.com/schema/routing"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/routing
                https://symfony.com/schema/routing/routing-1.0.xsd">

            <route id="share" path="/share/{token}" controller="App\Controller\DefaultController::share">
                <requirement key="token">.+</requirement>
            </route>
        </routes>

    .. code-block:: php

        // config/routes.php
        use App\Controller\DefaultController;
        use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;

        return function (RoutingConfigurator $routes) {
            $routes->add('share', '/share/{token}')
                ->controller([DefaultController::class, 'share'])
                ->requirements([
                    'token' => '.+',
                ])
            ;
        };

Note

If the route defines several parameter and you apply this permissive regular expression to all of them, you might get unexpected results. For example, if the route definition is /share/{path}/{token} and both path and token accept /. The token only get the last path and the rest of the match is matched by the first argument (path).

Note

If the route includes the special {_format} parameter, you shouldn't use the .+ requirement for the parameters that allow slashes. For example, if the pattern is /share/{token}.{_format} and {token} allows any character, the /share/foo/bar.json URL will consider foo/bar.json as the token and the format will be empty. This can be solved by replacing the .+ requirement by [^.]+ to allow any character except dots.

Route Groups and Prefixes

It's common for a group of routes to share some options (e.g. all routes related to the blog start with /blog) That's why Symfony includes a feature to share route configuration.

When defining routes as attributes or annotations, put the common configuration in the #[Route] attribute (or @Route annotation) of the controller class. In other routing formats, define the common configuration using options when importing the routes.

.. configuration-block::

    .. code-block:: php-annotations

        // src/Controller/BlogController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\HttpFoundation\Response;
        use Symfony\Component\Routing\Annotation\Route;

        /**
         * @Route("/blog", requirements={"_locale": "en|es|fr"}, name="blog_")
         */
        class BlogController extends AbstractController
        {
            /**
             * @Route("/{_locale}", name="index")
             */
            public function index(): Response
            {
                // ...
            }

            /**
             * @Route("/{_locale}/posts/{slug}", name="show")
             */
            public function show(Post $post): Response
            {
                // ...
            }
        }

    .. code-block:: php-attributes

        // src/Controller/BlogController.php
        namespace App\Controller;

        use Symfony\Component\Routing\Annotation\Route;

        #[Route('/blog', requirements: ['_locale' => 'en|es|fr'], name: 'blog_')]
        class BlogController
        {
            #[Route('/{_locale}', name: 'index')]
            public function index()
            {
                // ...
            }

            #[Route('/{_locale}/posts/{slug}', name: 'show')]
            public function show(Post $post)
            {
                // ...
            }
        }

    .. code-block:: yaml

        # config/routes/annotations.yaml
        controllers:
            resource: '../../src/Controller/'
            type: annotation
            # this is added to the beginning of all imported route URLs
            prefix: '/blog'
            # this is added to the beginning of all imported route names
            name_prefix: 'blog_'
            # these requirements are added to all imported routes
            requirements:
                _locale: 'en|es|fr'
            # An imported route with an empty URL will become "/blog/"
            # Uncomment this option to make that URL "/blog" instead
            # trailing_slash_on_root: false
            # you can optionally exclude some files/subdirectories when loading annotations
            # exclude: '../../src/Controller/{DebugEmailController}.php'

    .. code-block:: xml

        <!-- config/routes/annotations.xml -->
        <?xml version="1.0" encoding="UTF-8" ?>
        <routes xmlns="http://symfony.com/schema/routing"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/routing
                https://symfony.com/schema/routing/routing-1.0.xsd">

            <!--
                the 'prefix' value is added to the beginning of all imported route URLs
                the 'name-prefix' value is added to the beginning of all imported route names
                the 'exclude' option defines the files or subdirectories ignored when loading annotations
            -->
            <import resource="../../src/Controller/"
                type="annotation"
                prefix="/blog"
                name-prefix="blog_"
                exclude="../../src/Controller/{DebugEmailController}.php">
                <!-- these requirements are added to all imported routes -->
                <requirement key="_locale">en|es|fr</requirement>
            </import>

            <!-- An imported route with an empty URL will become "/blog/"
                 Uncomment this option to make that URL "/blog" instead -->
            <import resource="../../src/Controller/" type="annotation"
                    prefix="/blog"
                    trailing-slash-on-root="false">
                    <!-- ... -->
            </import>
        </routes>

    .. code-block:: php

        // config/routes/annotations.php
        use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;

        return function (RoutingConfigurator $routes) {
            // use the optional fourth argument of import() to exclude some files
            // or subdirectories when loading annotations
            $routes->import('../../src/Controller/', 'annotation')
                // this is added to the beginning of all imported route URLs
                ->prefix('/blog')
                // An imported route with an empty URL will become "/blog/"
                // Pass FALSE as the second argument to make that URL "/blog" instead
                // ->prefix('/blog', false)
                // this is added to the beginning of all imported route names
                ->namePrefix('blog_')
                // these requirements are added to all imported routes
                ->requirements(['_locale' => 'en|es|fr'])
            ;
        };

In this example, the route of the index() action will be called blog_index and its URL will be /blog/. The route of the show() action will be called blog_show and its URL will be /blog/{_locale}/posts/{slug}. Both routes will also validate that the _locale parameter matches the regular expression defined in the class annotation.

.. seealso::

    Symfony can :doc:`import routes from different sources </routing/custom_route_loader>`
    and you can even create your own route loader.

Getting the Route Name and Parameters

The Request object created by Symfony stores all the route configuration (such as the name and parameters) in the "request attributes". You can get this information in a controller via the Request object:

// src/Controller/BlogController.php
namespace App\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\Routing\Annotation\Route;

class BlogController extends AbstractController
{
    /**
     * @Route("/blog", name="blog_list")
     */
    public function list(Request $request): Response
    {
        $routeName = $request->attributes->get('_route');
        $routeParameters = $request->attributes->get('_route_params');

        // use this to get all the available attributes (not only routing ones):
        $allAttributes = $request->attributes->all();

        // ...
    }
}

You can get this information in services too injecting the request_stack service to :doc:`get the Request object in a service </service_container/request>`. In templates, use the :ref:`Twig global app variable <twig-app-variable>` to get the request and its attributes:

{% set route_name = app.request.attributes.get('_route') %}
{% set route_parameters = app.request.attributes.get('_route_params') %}

{# use this to get all the available attributes (not only routing ones) #}
{% set all_attributes = app.request.attributes.all %}

Special Routes

Symfony defines some special controllers to render templates and redirect to other routes from the route configuration so you don't have to create a controller action.

Rendering a Template Directly from a Route

Read the section about :ref:`rendering a template from a route <templates-render-from-route>` in the main article about Symfony templates.

Redirecting to URLs and Routes Directly from a Route

Use the RedirectController to redirect to other routes and URLs:

.. configuration-block::

    .. code-block:: yaml

        # config/routes.yaml
        doc_shortcut:
            path: /doc
            controller: Symfony\Bundle\FrameworkBundle\Controller\RedirectController
            defaults:
                route: 'doc_page'
                # optionally you can define some arguments passed to the route
                page: 'index'
                version: 'current'
                # redirections are temporary by default (code 302) but you can make them permanent (code 301)
                permanent: true
                # add this to keep the original query string parameters when redirecting
                keepQueryParams: true
                # add this to keep the HTTP method when redirecting. The redirect status changes
                # * for temporary redirects, it uses the 307 status code instead of 302
                # * for permanent redirects, it uses the 308 status code instead of 301
                keepRequestMethod: true

        legacy_doc:
            path: /legacy/doc
            controller: Symfony\Bundle\FrameworkBundle\Controller\RedirectController
            defaults:
                # this value can be an absolute path or an absolute URL
                path: 'https://legacy.example.com/doc'
                permanent: true

    .. code-block:: xml

        <!-- config/routes.xml -->
        <?xml version="1.0" encoding="UTF-8" ?>
        <routes xmlns="http://symfony.com/schema/routing"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/routing
                https://symfony.com/schema/routing/routing-1.0.xsd">

            <route id="doc_shortcut" path="/doc"
                   controller="Symfony\Bundle\FrameworkBundle\Controller\RedirectController">
                <default key="route">doc_page</default>
                <!-- optionally you can define some arguments passed to the route -->
                <default key="page">index</default>
                <default key="version">current</default>
                <!-- redirections are temporary by default (code 302) but you can make them permanent (code 301)-->
                <default key="permanent">true</default>
                <!-- add this to keep the original query string parameters when redirecting -->
                <default key="keepQueryParams">true</default>
                <!-- add this to keep the HTTP method when redirecting. The redirect status changes:
                     * for temporary redirects, it uses the 307 status code instead of 302
                     * for permanent redirects, it uses the 308 status code instead of 301 -->
                <default key="keepRequestMethod">true</default>
            </route>

            <route id="legacy_doc" path="/legacy/doc"
                   controller="Symfony\Bundle\FrameworkBundle\Controller\RedirectController">
                <!-- this value can be an absolute path or an absolute URL -->
                <default key="path">https://legacy.example.com/doc</default>
                <!-- redirections are temporary by default (code 302) but you can make them permanent (code 301)-->
                <default key="permanent">true</default>
            </route>
        </routes>

    .. code-block:: php

        // config/routes.php
        use App\Controller\DefaultController;
        use Symfony\Bundle\FrameworkBundle\Controller\RedirectController;
        use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;

        return function (RoutingConfigurator $routes) {
            $routes->add('doc_shortcut', '/doc')
                ->controller(RedirectController::class)
                 ->defaults([
                    'route' => 'doc_page',
                    // optionally you can define some arguments passed to the route
                    'page' => 'index',
                    'version' => 'current',
                    // redirections are temporary by default (code 302) but you can make them permanent (code 301)
                    'permanent' => true,
                    // add this to keep the original query string parameters when redirecting
                    'keepQueryParams' => true,
                    // add this to keep the HTTP method when redirecting. The redirect status changes:
                    // * for temporary redirects, it uses the 307 status code instead of 302
                    // * for permanent redirects, it uses the 308 status code instead of 301
                    'keepRequestMethod' => true,
                ])
            ;

            $routes->add('legacy_doc', '/legacy/doc')
                ->controller(RedirectController::class)
                 ->defaults([
                    // this value can be an absolute path or an absolute URL
                    'path' => 'https://legacy.example.com/doc',
                    // redirections are temporary by default (code 302) but you can make them permanent (code 301)
                    'permanent' => true,
                ])
            ;
        };

Tip

Symfony also provides some utilities to :ref:`redirect inside controllers <controller-redirect>`

Redirecting URLs with Trailing Slashes

Historically, URLs have followed the UNIX convention of adding trailing slashes for directories (e.g. https://example.com/foo/) and removing them to refer to files (https://example.com/foo). Although serving different contents for both URLs is OK, nowadays it's common to treat both URLs as the same URL and redirect between them.

Symfony follows this logic to redirect between URLs with and without trailing slashes (but only for GET and HEAD requests):

Route URL If the requested URL is /foo If the requested URL is /foo/
/foo It matches (200 status response) It makes a 301 redirect to /foo
/foo/ It makes a 301 redirect to /foo/ It matches (200 status response)

Sub-Domain Routing

Routes can configure a host option to require that the HTTP host of the incoming requests matches some specific value. In the following example, both routes match the same path (/) but one of them only responds to a specific host name:

.. configuration-block::

    .. code-block:: php-annotations

        // src/Controller/MainController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\HttpFoundation\Response;
        use Symfony\Component\Routing\Annotation\Route;

        class MainController extends AbstractController
        {
            /**
             * @Route("/", name="mobile_homepage", host="m.example.com")
             */
            public function mobileHomepage(): Response
            {
                // ...
            }

            /**
             * @Route("/", name="homepage")
             */
            public function homepage(): Response
            {
                // ...
            }
        }

    .. code-block:: php-attributes

        // src/Controller/MainController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\Routing\Annotation\Route;

        class MainController extends AbstractController
        {
            #[Route('/', name: 'mobile_homepage', host: 'm.example.com')]
            public function mobileHomepage()
            {
                // ...
            }

            #[Route('/', name: 'homepage')]
            public function homepage()
            {
                // ...
            }
        }

    .. code-block:: yaml

        # config/routes.yaml
        mobile_homepage:
            path:       /
            host:       m.example.com
            controller: App\Controller\MainController::mobileHomepage

        homepage:
            path:       /
            controller: App\Controller\MainController::homepage

    .. code-block:: xml

        <!-- config/routes.xml -->
        <?xml version="1.0" encoding="UTF-8" ?>
        <routes xmlns="http://symfony.com/schema/routing"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/routing
                https://symfony.com/schema/routing/routing-1.0.xsd">

            <route id="mobile_homepage"
                path="/"
                host="m.example.com"
                controller="App\Controller\MainController::mobileHomepage"/>

            <route id="homepage" path="/" controller="App\Controller\MainController::homepage"/>
        </routes>

    .. code-block:: php

        // config/routes.php
        use App\Controller\MainController;
        use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;

        return function (RoutingConfigurator $routes) {
            $routes->add('mobile_homepage', '/')
                ->controller([MainController::class, 'mobileHomepage'])
                ->host('m.example.com')
            ;
            $routes->add('homepage', '/')
                ->controller([MainController::class, 'homepage'])
            ;
        };


The value of the host option can include parameters (which is useful in multi-tenant applications) and these parameters can be validated too with requirements:

.. configuration-block::

    .. code-block:: php-annotations

        // src/Controller/MainController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\HttpFoundation\Response;
        use Symfony\Component\Routing\Annotation\Route;

        class MainController extends AbstractController
        {
            /**
             * @Route(
             *     "/",
             *     name="mobile_homepage",
             *     host="{subdomain}.example.com",
             *     defaults={"subdomain"="m"},
             *     requirements={"subdomain"="m|mobile"}
             * )
             */
            public function mobileHomepage(): Response
            {
                // ...
            }

            /**
             * @Route("/", name="homepage")
             */
            public function homepage(): Response
            {
                // ...
            }
        }

    .. code-block:: php-attributes

        // src/Controller/MainController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\Routing\Annotation\Route;

        class MainController extends AbstractController
        {
            #[Route(
                '/',
                name: 'mobile_homepage',
                host: '{subdomain}.example.com',
                defaults: ['subdomain' => 'm'],
                requirements: ['subdomain' => 'm|mobile'],
            )]
            public function mobileHomepage()
            {
                // ...
            }

            #[Route('/', name: 'homepage')]
            public function homepage()
            {
                // ...
            }
        }

    .. code-block:: yaml

        # config/routes.yaml
        mobile_homepage:
            path:       /
            host:       "{subdomain}.example.com"
            controller: App\Controller\MainController::mobileHomepage
            defaults:
                subdomain: m
            requirements:
                subdomain: m|mobile

        homepage:
            path:       /
            controller: App\Controller\MainController::homepage

    .. code-block:: xml

        <!-- config/routes.xml -->
        <?xml version="1.0" encoding="UTF-8" ?>
        <routes xmlns="http://symfony.com/schema/routing"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/routing
                https://symfony.com/schema/routing/routing-1.0.xsd">

            <route id="mobile_homepage"
                path="/"
                host="{subdomain}.example.com"
                controller="App\Controller\MainController::mobileHomepage">
                <default key="subdomain">m</default>
                <requirement key="subdomain">m|mobile</requirement>
            </route>

            <route id="homepage" path="/" controller="App\Controller\MainController::homepage"/>
        </routes>

    .. code-block:: php

        // config/routes.php
        use App\Controller\MainController;
        use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;

        return function (RoutingConfigurator $routes) {
            $routes->add('mobile_homepage', '/')
                ->controller([MainController::class, 'mobileHomepage'])
                ->host('{subdomain}.example.com')
                ->defaults([
                    'subdomain' => 'm',
                ])
                ->requirements([
                    'subdomain' => 'm|mobile',
                ])
            ;
            $routes->add('homepage', '/')
                ->controller([MainController::class, 'homepage'])
            ;
        };

In the above example, the subdomain parameter defines a default value because otherwise you need to include a domain value each time you generate a URL using these routes.

Tip

You can also set the host option when :ref:`importing routes <routing-route-groups>` to make all of them require that host name.

Note

When using sub-domain routing, you must set the Host HTTP headers in :doc:`functional tests </testing>` or routes won't match:

$crawler = $client->request(
    'GET',
    '/',
    [],
    [],
    ['HTTP_HOST' => 'm.example.com']
    // or get the value from some container parameter:
    // ['HTTP_HOST' => 'm.' . $client->getContainer()->getParameter('domain')]
);

Localized Routes (i18n)

If your application is translated into multiple languages, each route can define a different URL per each :doc:`translation locale </translation/locale>`. This avoids the need for duplicating routes, which also reduces the potential bugs:

.. configuration-block::

    .. code-block:: php-annotations

        // src/Controller/CompanyController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\HttpFoundation\Response;
        use Symfony\Component\Routing\Annotation\Route;

        class CompanyController extends AbstractController
        {
            /**
             * @Route({
             *     "en": "/about-us",
             *     "nl": "/over-ons"
             * }, name="about_us")
             */
            public function about(): Response
            {
                // ...
            }
        }

    .. code-block:: php-attributes

        // src/Controller/CompanyController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\Routing\Annotation\Route;

        class CompanyController extends AbstractController
        {
            #[Route(path: [
                'en' => '/about-us',
                'nl' => '/over-ons'
            ], name: 'about_us')]
            public function about()
            {
                // ...
            }
        }

    .. code-block:: yaml

        # config/routes.yaml
        about_us:
            path:
                en: /about-us
                nl: /over-ons
            controller: App\Controller\CompanyController::about

    .. code-block:: xml

        <!-- config/routes.xml -->
        <?xml version="1.0" encoding="UTF-8" ?>
        <routes xmlns="http://symfony.com/schema/routing"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/routing
                https://symfony.com/schema/routing/routing-1.0.xsd">

            <route id="about_us" controller="App\Controller\CompanyController::about">
                <path locale="en">/about-us</path>
                <path locale="nl">/over-ons</path>
            </route>
        </routes>

    .. code-block:: php

        // config/routes.php
        use App\Controller\CompanyController;
        use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;

        return function (RoutingConfigurator $routes) {
            $routes->add('about_us', [
                'en' => '/about-us',
                'nl' => '/over-ons',
            ])
                ->controller([CompanyController::class, 'about'])
            ;
        };

Note

When using PHP attributes for localized routes, you have to use the path named parameter to specify the array of paths.

When a localized route is matched, Symfony uses the same locale automatically during the entire request.

Tip

When the application uses full "language + territory" locales (e.g. fr_FR, fr_BE), if the URLs are the same in all related locales, routes can use only the language part (e.g. fr) to avoid repeating the same URLs.

A common requirement for internationalized applications is to prefix all routes with a locale. This can be done by defining a different prefix for each locale (and setting an empty prefix for your default locale if you prefer it):

.. configuration-block::

    .. code-block:: yaml

        # config/routes/annotations.yaml
        controllers:
            resource: '../../src/Controller/'
            type: annotation
            prefix:
                en: '' # don't prefix URLs for English, the default locale
                nl: '/nl'

    .. code-block:: xml

        <!-- config/routes/annotations.xml -->
        <?xml version="1.0" encoding="UTF-8" ?>
        <routes xmlns="http://symfony.com/schema/routing"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/routing
                https://symfony.com/schema/routing/routing-1.0.xsd">

            <import resource="../../src/Controller/" type="annotation">
                <!-- don't prefix URLs for English, the default locale -->
                <prefix locale="en"></prefix>
                <prefix locale="nl">/nl</prefix>
            </import>
        </routes>

    .. code-block:: php

        // config/routes/annotations.php
        use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;

        return function (RoutingConfigurator $routes) {
            $routes->import('../../src/Controller/', 'annotation')
                ->prefix([
                    // don't prefix URLs for English, the default locale
                    'en' => '',
                    'nl' => '/nl'
                ])
            ;
        };

Stateless Routes

.. versionadded:: 5.1

    The ``stateless`` option was introduced in Symfony 5.1.

Sometimes, when an HTTP response should be cached, it is important to ensure that can happen. However, whenever session is started during a request, Symfony turns the response into a private non-cacheable response.

For details, see :doc:`/http_cache`.

Routes can configure a stateless boolean option in order to declare that the session shouldn't be used when matching a request:

.. configuration-block::

    .. code-block:: php-annotations

        // src/Controller/MainController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\Routing\Annotation\Route;

        class MainController extends AbstractController
        {
            /**
             * @Route("/", name="homepage", stateless=true)
             */
            public function homepage()
            {
                // ...
            }
        }

    .. code-block:: php-attributes

        // src/Controller/MainController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\Routing\Annotation\Route;

        class MainController extends AbstractController
        {
            #[Route('/', name: 'homepage', stateless: true)]
            public function homepage()
            {
                // ...
            }
        }

    .. code-block:: yaml

        # config/routes.yaml
        homepage:
            controller: App\Controller\MainController::homepage
            path: /
            stateless: true

    .. code-block:: xml

        <!-- config/routes.xml -->
        <?xml version="1.0" encoding="UTF-8" ?>
        <routes xmlns="http://symfony.com/schema/routing"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/routing
                https://symfony.com/schema/routing/routing-1.0.xsd">
            <route id="homepage" controller="App\Controller\MainController::homepage" path="/" stateless="true"/>
        </routes>

    .. code-block:: php

        // config/routes.php
        use App\Controller\MainController;
        use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;

        return function (RoutingConfigurator $routes) {
            $routes->add('homepage', '/')
                ->controller([MainController::class, 'homepage'])
                ->stateless()
            ;
        };

Now, if the session is used, the application will report it based on your kernel.debug parameter: * enabled: will throw an :class:`Symfony\\Component\\HttpKernel\\Exception\\UnexpectedSessionUsageException` exception * disabled: will log a warning

It will help you understand and hopefully fixing unexpected behavior in your application.

Generating URLs

Routing systems are bidirectional: 1) they associate URLs with controllers (as explained in the previous sections); 2) they generate URLs for a given route. Generating URLs from routes allows you to not write the <a href="..."> values manually in your HTML templates. Also, if the URL of some route changes, you only have to update the route configuration and all links will be updated.

To generate a URL, you need to specify the name of the route (e.g. blog_show) and the values of the parameters defined by the route (e.g. slug = my-blog-post).

For that reason each route has an internal name that must be unique in the application. If you don't set the route name explicitly with the name option, Symfony generates an automatic name based on the controller and action.

Generating URLs in Controllers

If your controller extends from the :ref:`AbstractController <the-base-controller-class-services>`, use the generateUrl() helper:

// src/Controller/BlogController.php
namespace App\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\Routing\Annotation\Route;
use Symfony\Component\Routing\Generator\UrlGeneratorInterface;

class BlogController extends AbstractController
{
    /**
     * @Route("/blog", name="blog_list")
     */
    public function list(): Response
    {
        // generate a URL with no route arguments
        $signUpPage = $this->generateUrl('sign_up');

        // generate a URL with route arguments
        $userProfilePage = $this->generateUrl('user_profile', [
            'username' => $user->getUsername(),
        ]);

        // generated URLs are "absolute paths" by default. Pass a third optional
        // argument to generate different URLs (e.g. an "absolute URL")
        $signUpPage = $this->generateUrl('sign_up', [], UrlGeneratorInterface::ABSOLUTE_URL);

        // when a route is localized, Symfony uses by default the current request locale
        // pass a different '_locale' value if you want to set the locale explicitly
        $signUpPageInDutch = $this->generateUrl('sign_up', ['_locale' => 'nl']);

        // ...
    }
}

Note

If you pass to the generateUrl() method some parameters that are not part of the route definition, they are included in the generated URL as a query string::

$this->generateUrl('blog', ['page' => 2, 'category' => 'Symfony']);
// the 'blog' route only defines the 'page' parameter; the generated URL is:
// /blog/2?category=Symfony

If your controller does not extend from AbstractController, you'll need to :ref:`fetch services in your controller <controller-accessing-services>` and follow the instructions of the next section.

Generating URLs in Services

Inject the router Symfony service into your own services and use its generate() method. When using :doc:`service autowiring </service_container/autowiring>` you only need to add an argument in the service constructor and type-hint it with the :class:`Symfony\\Component\\Routing\\Generator\\UrlGeneratorInterface` class:

// src/Service/SomeService.php
namespace App\Service;

use Symfony\Component\Routing\Generator\UrlGeneratorInterface;

class SomeService
{
    private $router;

    public function __construct(UrlGeneratorInterface $router)
    {
        $this->router = $router;
    }

    public function someMethod()
    {
        // ...

        // generate a URL with no route arguments
        $signUpPage = $this->router->generate('sign_up');

        // generate a URL with route arguments
        $userProfilePage = $this->router->generate('user_profile', [
            'username' => $user->getUsername(),
        ]);

        // generated URLs are "absolute paths" by default. Pass a third optional
        // argument to generate different URLs (e.g. an "absolute URL")
        $signUpPage = $this->router->generate('sign_up', [], UrlGeneratorInterface::ABSOLUTE_URL);

        // when a route is localized, Symfony uses by default the current request locale
        // pass a different '_locale' value if you want to set the locale explicitly
        $signUpPageInDutch = $this->router->generate('sign_up', ['_locale' => 'nl']);
    }
}

Generating URLs in Templates

Read the section about :ref:`creating links between pages <templates-link-to-pages>` in the main article about Symfony templates.

Generating URLs in JavaScript

If your JavaScript code is included in a Twig template, you can use the path() and url() Twig functions to generate the URLs and store them in JavaScript variables. The escape() filter is needed to escape any non-JavaScript-safe values:

<script>
    const route = "{{ path('blog_show', {slug: 'my-blog-post'})|escape('js') }}";
</script>

If you need to generate URLs dynamically or if you are using pure JavaScript code, this solution doesn't work. In those cases, consider using the FOSJsRoutingBundle.

Generating URLs in Commands

Generating URLs in commands works the same as :ref:`generating URLs in services <routing-generating-urls-in-services>`. The only difference is that commands are not executed in the HTTP context. Therefore, if you generate absolute URLs, you'll get http://localhost/ as the host name instead of your real host name.

The solution is to configure the default_uri option to define the "request context" used by commands when they generate URLs:

.. configuration-block::

    .. code-block:: yaml

        # config/packages/routing.yaml
        framework:
            router:
                # ...
                default_uri: 'https://example.org/my/path/'

    .. code-block:: xml

        <!-- config/packages/routing.xml -->
        <?xml version="1.0" encoding="UTF-8" ?>
        <container xmlns="http://symfony.com/schema/dic/services"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xmlns:framework="http://symfony.com/schema/dic/symfony"
            xsi:schemaLocation="http://symfony.com/schema/dic/services
                https://symfony.com/schema/dic/services/services-1.0.xsd
                http://symfony.com/schema/dic/symfony
                https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">

            <framework:config>
                <framework:router default-uri="https://example.org/my/path/">
                    <!-- ... -->
                </framework:router>
            </framework:config>
        </container>

    .. code-block:: php

        // config/packages/routing.php
        $container->loadFromExtension('framework', [
            'router' => [
                // ...
                'default_uri' => "https://example.org/my/path/",
            ],
        ]);

.. versionadded:: 5.1

    The ``default_uri`` option was introduced in Symfony 5.1.

Now you'll get the expected results when generating URLs in your commands:

// src/Command/SomeCommand.php
namespace App\Command;

use Symfony\Component\Console\Command\Command;
use Symfony\Component\Console\Input\InputInterface;
use Symfony\Component\Console\Output\OutputInterface;
use Symfony\Component\Routing\Generator\UrlGeneratorInterface;
use Symfony\Component\Routing\RouterInterface;
// ...

class SomeCommand extends Command
{
    private $router;

    public function __construct(RouterInterface $router)
    {
        parent::__construct();

        $this->router = $router;
    }

    protected function execute(InputInterface $input, OutputInterface $output): int
    {
        // generate a URL with no route arguments
        $signUpPage = $this->router->generate('sign_up');

        // generate a URL with route arguments
        $userProfilePage = $this->router->generate('user_profile', [
            'username' => $user->getUsername(),
        ]);

        // generated URLs are "absolute paths" by default. Pass a third optional
        // argument to generate different URLs (e.g. an "absolute URL")
        $signUpPage = $this->router->generate('sign_up', [], UrlGeneratorInterface::ABSOLUTE_URL);

        // when a route is localized, Symfony uses by default the current request locale
        // pass a different '_locale' value if you want to set the locale explicitly
        $signUpPageInDutch = $this->router->generate('sign_up', ['_locale' => 'nl']);

        // ...
    }
}

Note

By default, the URLs generated for web assets use the same default_uri value, but you can change it with the asset.request_context.base_path and asset.request_context.secure container parameters.

Checking if a Route Exists

In highly dynamic applications, it may be necessary to check whether a route exists before using it to generate a URL. In those cases, don't use the :method:`Symfony\\Component\\Routing\\Router::getRouteCollection` method because that regenerates the routing cache and slows down the application.

Instead, try to generate the URL and catch the :class:`Symfony\\Component\\Routing\\Exception\\RouteNotFoundException` thrown when the route doesn't exist:

use Symfony\Component\Routing\Exception\RouteNotFoundException;

// ...

try {
    $url = $this->router->generate($routeName, $routeParameters);
} catch (RouteNotFoundException $e) {
    // the route is not defined...
}

Forcing HTTPS on Generated URLs

By default, generated URLs use the same HTTP scheme as the current request. In console commands, where there is no HTTP request, URLs use http by default. You can change this per command (via the router's getContext() method) or globally with these configuration parameters:

.. configuration-block::

    .. code-block:: yaml

        # config/services.yaml
        parameters:
            router.request_context.scheme: 'https'
            asset.request_context.secure: true

    .. code-block:: xml

        <!-- config/services.xml -->
        <?xml version="1.0" encoding="UTF-8"?>
        <container xmlns="http://symfony.com/schema/dic/services"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/dic/services
                https://symfony.com/schema/dic/services/services-1.0.xsd">

            <parameters>
                <parameter key="router.request_context.scheme">https</parameter>
                <parameter key="asset.request_context.secure">true</parameter>
            </parameters>

        </container>

    .. code-block:: php

        // config/services.php
        $container->setParameter('router.request_context.scheme', 'https');
        $container->setParameter('asset.request_context.secure', true);

Outside of console commands, use the schemes option to define the scheme of each route explicitly:

.. configuration-block::

    .. code-block:: php-annotations

        // src/Controller/SecurityController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\HttpFoundation\Response;
        use Symfony\Component\Routing\Annotation\Route;

        class SecurityController extends AbstractController
        {
            /**
             * @Route("/login", name="login", schemes={"https"})
             */
            public function login(): Response
            {
                // ...
            }
        }

    .. code-block:: php-attributes

        // src/Controller/SecurityController.php
        namespace App\Controller;

        use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
        use Symfony\Component\Routing\Annotation\Route;

        class SecurityController extends AbstractController
        {
            #[Route('/login', name: 'login', schemes: ['https'])]
            public function login()
            {
                // ...
            }
        }

    .. code-block:: yaml

        # config/routes.yaml
        login:
            path:       /login
            controller: App\Controller\SecurityController::login
            schemes:    [https]

    .. code-block:: xml

        <!-- config/routes.xml -->
        <?xml version="1.0" encoding="UTF-8" ?>

        <routes xmlns="http://symfony.com/schema/routing"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/routing https://symfony.com/schema/routing/routing-1.0.xsd">

            <route id="login" path="/login" schemes="https"
                   controller="App\Controller\SecurityController::login"/>
        </routes>

    .. code-block:: php

        // config/routes.php
        use App\Controller\SecurityController;
        use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;

        return function (RoutingConfigurator $routes) {
            $routes->add('login', '/login')
                ->controller([SecurityController::class, 'login'])
                ->schemes(['https'])
            ;
        };

The URL generated for the login route will always use HTTPS. This means that when using the path() Twig function to generate URLs, you may get an absolute URL instead of a relative URL if the HTTP scheme of the original request is different from the scheme used by the route:

{# if the current scheme is HTTPS, generates a relative URL: /login #}
{{ path('login') }}

{# if the current scheme is HTTP, generates an absolute URL to change
   the scheme: https://example.com/login #}
{{ path('login') }}

The scheme requirement is also enforced for incoming requests. If you try to access the /login URL with HTTP, you will automatically be redirected to the same URL, but with the HTTPS scheme.

If you want to force a group of routes to use HTTPS, you can define the default scheme when importing them. The following example forces HTTPS on all routes defined as annotations:

.. configuration-block::

    .. code-block:: yaml

        # config/routes/annotations.yaml
        controllers:
            resource: '../../src/Controller/'
            type: annotation
            defaults:
                schemes: [https]

    .. code-block:: xml

        <!-- config/routes/annotations.xml -->
        <?xml version="1.0" encoding="UTF-8" ?>
        <routes xmlns="http://symfony.com/schema/routing"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/routing
                https://symfony.com/schema/routing/routing-1.0.xsd">

            <import resource="../../src/Controller/" type="annotation">
                <default key="schemes">HTTPS</default>
            </import>
        </routes>

    .. code-block:: php

        // config/routes/annotations.php
        use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;

        return function (RoutingConfigurator $routes) {
            $routes->import('../../src/Controller/', 'annotation')
                ->schemes(['https'])
            ;
        };

Note

The Security component provides :doc:`another way to enforce HTTP or HTTPS </security/force_https>` via the requires_channel setting.

Troubleshooting

Here are some common errors you might see while working with routing:

Controller "App\Controller\BlogController::show()" requires that you provide a value for the "$slug" argument.

This happens when your controller method has an argument (e.g. $slug):

public function show(string $slug): Response
{
    // ...
}

But your route path does not have a {slug} parameter (e.g. it is /blog/show). Add a {slug} to your route path: /blog/show/{slug} or give the argument a default value (i.e. $slug = null).

Some mandatory parameters are missing ("slug") to generate a URL for route "blog_show".

This means that you're trying to generate a URL to the blog_show route but you are not passing a slug value (which is required, because it has a {slug} parameter in the route path). To fix this, pass a slug value when generating the route:

$this->generateUrl('blog_show', ['slug' => 'slug-value']);

or, in Twig:

{{ path('blog_show', {slug: 'slug-value'}) }}

Learn more about Routing

.. toctree::
    :hidden:

    controller

.. toctree::
    :maxdepth: 1
    :glob:

    routing/*