This library provides a simple way to convert a string of simple values to their PHP runtime equivalents.

This library will parse the following types of values:

• Numbers
• Strings
• Arrays
• Associative arrays
• true, false, null
• Built-in PHP constants

Unknown types will return null as their value.

Installation

This library can be installed with composer:

composer require stillat/primitives

Example Usage

To use the library, create a new instance of the Parser class and call the parseString method:

<?php

use Stillat\Primitives\Parser;

$parser = new Parser();

$result = $parser->parseString('[1, 2, 3], "some-string", "another", ["one" => 1, "two" => 2]');

would produce the following runtime result:

array(4) {
  [0] =>
  array(3) {
    [0] =>
    int(1)
    [1] =>
    int(2)
    [2] =>
    int(3)
  }
  [1] =>
  string(11) "some-string"
  [2] =>
  string(7) "another"
  [3] =>
  array(2) {
    'one' =>
    int(1)
    'two' =>
    int(2)
  }
}

This library can also parse basic method details using the parseMethod method:

<?php

use Stillat\Primitives\Parser;

$parser = new Parser();

$result = $parser->parseMethod('methodName([1, 2, 3])');

would produce the following runtime result:

array(2) {
  [0] =>
  string(10) "methodName"
  [1] =>
  array(1) {
    [0] =>
    array(3) {
      [0] =>
      int(1)
      [1] =>
      int(2)
      [2] =>
      int(3)
    }
  }
}

Invalid input will produce a null value.

Parsing Nested Methods

A more advanced alternative of parseMethod is the parseMethods method:

use Stillat\Primitives\Parser;

$parser = new Parser();

$result = $parser->parseMethods("randomElements(['a', 'b', 'c', 'd', 'e'], rand(1, 5))"); 

Detected method calls will be returned as instances of Stillat\Primitives\MethodCall. Each instance of this class will contain the original method's name, as well as the parsed (and evaluated) runtime arguments. parseMethods will not run any methods for you.

Executing Runtime Methods

Primitives provides a utility MethodRunner class that can be used to execute the results of the parseMethods on any target class:

<?php

use Stillat\Primitives\Parser;
use Stillat\Primitives\MethodRunner;

$parser = new Parser();
$runner = new MethodRunner();

class MyClass {

    public function sayHello($name)
    {
        return 'Hello, '.$name;
    }

}

$myClassInstance = new MyClass();

$methods = $parser->parseMethods("sayHello('Dave')");
$result = $runner->run($methods, $myClassInstance);

After the above code has executed, $result would contain the value Hello, Dave.

Important notes when using MethodRunner:

• There must only be one root method call
• If there is more than one root element, the run method returns null
• MethodRunner does not check for method existence, allowing __call to be invoked

Calling Native PHP Functions

The internal method runner does not support calling native PHP functions. However, we can create a class instance that can (and utilize whatever logic is appropriate for the current project to determine what is a "safe" function to call):

<?php

use Stillat\Primitives\Parser;
use Stillat\Primitives\MethodRunner;

$parser = new Parser();
$runner = new MethodRunner();

class Greeter {

    public function sayHello($name)
    {
        return 'Hello, '.$name;
    }

}

class MethodTarget
{

    protected $instance;
    protected $safePhpFunctions = [
        'strtoupper'
    ];

    public function __construct()
    {
        $this->instance = new Greeter();
    }

    public function __call($name, $arguments)
    {
        // Replace with whatever logic makes sense. This approach
        // utilizes an allowed list of functions, but using
        // something like function_exists also works.
        if (in_array($name, $this->safePhpFunctions)) {
            return call_user_func($name, ...$arguments);
        }

        return call_user_func([$this->instance, $name], ...$arguments);
    }

}

$instance = new MethodTarget();

$result = $parser->parseMethods('sayHello(strtoupper("this is lowercase"))');

$methodResult = $runner->run($result, $instance);

After the above code has executed, $methodResult would contain the value Hello, THIS IS LOWERCASE. This approach works because we are making use of PHP's __call magic method to perform method overloading. When we attempt to call a method on our class instance that does not exist, the __call method will receive the method name and arguments. If the list of safe functions contains the incoming method name, we will invoke it and return the results with the original arguments. If our safe list does not contain the function, we default to attempting to call it on our target class instance.

Context Variables

You may also supply an array of contextual data that can be used when evaluating the input string. Context variables utilize the $ syntax. The variable name in the input string will be replaced with their actual values once evaluated:

<?php

use Stillat\Primitives\Parser;

$parser = new Parser();

$context = [
    'name' => 'Dave',
    'city' => 'Anywhere'
];

$result = $parser->parseString('[$name, $city]', $context);

Once the previous example has executed, $result would contain a value similar to:

array(1) {
  [0] =>
  array(2) {
    [0] =>
    string(4) "Dave"
    [1] =>
    string(8) "Anywhere"
  }
}

Nested variable paths can be utilized by using PHP's property fetcher syntax (array accessor syntax is not supported):

<?php

use Stillat\Primitives\Parser;

$parser = new Parser();

$context = [
    'nested' => [
        'arrays' => [
            'test' => [
                'name' => 'Dave',
                'city' => 'Anywhere'
            ]
        ]
    ]
];

$result = $parser->parseString('[$nested->arrays->test->name,' .
    '$nested->arrays->test->city]', $context);

Like before, the $result variable would contain a value similar to the following:

array(1) {
  [0] =>
  array(2) {
    [0] =>
    string(4) "Dave"
    [1] =>
    string(8) "Anywhere"
  }
}

License

MIT License. See LICENSE.MD