diff --git a/DataSource/Extension/Configuration/EventSubscriber/ConfigurationBuilder.php b/DataSource/Extension/Configuration/EventSubscriber/ConfigurationBuilder.php
index bcf12ca..54e682e 100644
--- a/DataSource/Extension/Configuration/EventSubscriber/ConfigurationBuilder.php
+++ b/DataSource/Extension/Configuration/EventSubscriber/ConfigurationBuilder.php
@@ -7,6 +7,8 @@
  * file that was distributed with this source code.
  */
 
+declare(strict_types=1);
+
 namespace FSi\Bundle\DataSourceBundle\DataSource\Extension\Configuration\EventSubscriber;
 
 use FSi\Component\DataSource\DataSourceInterface;
diff --git a/DataSource/Extension/Symfony/Core/CoreExtension.php b/DataSource/Extension/Symfony/Core/CoreExtension.php
index 41d40e8..c053b3d 100644
--- a/DataSource/Extension/Symfony/Core/CoreExtension.php
+++ b/DataSource/Extension/Symfony/Core/CoreExtension.php
@@ -7,14 +7,12 @@
  * file that was distributed with this source code.
  */
 
+declare(strict_types=1);
+
 namespace FSi\Bundle\DataSourceBundle\DataSource\Extension\Symfony\Core;
 
 use FSi\Component\DataSource\DataSourceAbstractExtension;
 
-/**
- * Main extension for all Symfony based extensions. Its main purpose is to
- * replace binded Request object into array.
- */
 class CoreExtension extends DataSourceAbstractExtension
 {
     public function loadSubscribers()
diff --git a/DataSource/Extension/Symfony/Core/EventSubscriber/BindParameters.php b/DataSource/Extension/Symfony/Core/EventSubscriber/BindParameters.php
index d8540c2..a86f278 100644
--- a/DataSource/Extension/Symfony/Core/EventSubscriber/BindParameters.php
+++ b/DataSource/Extension/Symfony/Core/EventSubscriber/BindParameters.php
@@ -7,6 +7,8 @@
  * file that was distributed with this source code.
  */
 
+declare(strict_types=1);
+
 namespace FSi\Bundle\DataSourceBundle\DataSource\Extension\Symfony\Core\EventSubscriber;
 
 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
diff --git a/DataSource/Extension/Symfony/DependencyInjection/Driver/DriverExtension.php b/DataSource/Extension/Symfony/DependencyInjection/Driver/DriverExtension.php
index edd6830..820c6e2 100644
--- a/DataSource/Extension/Symfony/DependencyInjection/Driver/DriverExtension.php
+++ b/DataSource/Extension/Symfony/DependencyInjection/Driver/DriverExtension.php
@@ -7,16 +7,16 @@
  * file that was distributed with this source code.
  */
 
+declare(strict_types=1);
+
 namespace FSi\Bundle\DataSourceBundle\DataSource\Extension\Symfony\DependencyInjection\Driver;
 
 use FSi\Component\DataSource\Driver\DriverExtensionInterface;
 use FSi\Component\DataSource\Field\FieldExtensionInterface;
 use FSi\Component\DataSource\Field\FieldTypeInterface;
+use InvalidArgumentException;
 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
 
-/**
- * DependencyInjection extension loads various types of extensions from Symfony's service container.
- */
 class DriverExtension implements DriverExtensionInterface
 {
     /**
@@ -49,7 +49,7 @@ public function __construct(string $driverType, array $fieldTypes, array $fieldE
 
         foreach ($fieldExtensions as $fieldExtension) {
             foreach ($fieldExtension->getExtendedFieldTypes() as $extendedFieldType) {
-                if (!array_key_exists($extendedFieldType, $this->fieldExtensions)) {
+                if (false === array_key_exists($extendedFieldType, $this->fieldExtensions)) {
                     $this->fieldExtensions[$extendedFieldType] = [];
                 }
 
@@ -72,8 +72,8 @@ public function hasFieldType($type)
 
     public function getFieldType($type)
     {
-        if (!array_key_exists($type, $this->fieldTypes)) {
-            throw new \InvalidArgumentException(sprintf('The field type "%s" is not registered within the service container.', $type));
+        if (false === array_key_exists($type, $this->fieldTypes)) {
+            throw new InvalidArgumentException(sprintf('The field type "%s" is not registered within the service container.', $type));
         }
 
         return $this->fieldTypes[$type];
@@ -86,7 +86,7 @@ public function hasFieldTypeExtensions($type)
 
     public function getFieldTypeExtensions($type)
     {
-        if (!array_key_exists($type, $this->fieldExtensions)) {
+        if (false === array_key_exists($type, $this->fieldExtensions)) {
             return [];
         }
 
diff --git a/DataSourceBundle.php b/DataSourceBundle.php
index 90261e6..6f1664e 100644
--- a/DataSourceBundle.php
+++ b/DataSourceBundle.php
@@ -7,6 +7,8 @@
  * file that was distributed with this source code.
  */
 
+declare(strict_types=1);
+
 namespace FSi\Bundle\DataSourceBundle;
 
 use Symfony\Component\HttpKernel\Bundle\Bundle;
diff --git a/DependencyInjection/Compiler/DataSourcePass.php b/DependencyInjection/Compiler/DataSourcePass.php
index 4b35c30..17a1550 100644
--- a/DependencyInjection/Compiler/DataSourcePass.php
+++ b/DependencyInjection/Compiler/DataSourcePass.php
@@ -7,17 +7,19 @@
  * file that was distributed with this source code.
  */
 
+declare(strict_types=1);
+
 namespace FSi\Bundle\DataSourceBundle\DependencyInjection\Compiler;
 
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
 use Symfony\Component\DependencyInjection\Reference;
 
-class DataSourcePass implements CompilerPassInterface
+final class DataSourcePass implements CompilerPassInterface
 {
     public function process(ContainerBuilder $container)
     {
-        if (!$container->hasDefinition('datasource.extension')) {
+        if (false === $container->hasDefinition('datasource.extension')) {
             return;
         }
 
diff --git a/DependencyInjection/Compiler/TemplatePathPass.php b/DependencyInjection/Compiler/TemplatePathPass.php
index 6afd069..cf13d1a 100644
--- a/DependencyInjection/Compiler/TemplatePathPass.php
+++ b/DependencyInjection/Compiler/TemplatePathPass.php
@@ -7,6 +7,8 @@
  * file that was distributed with this source code.
  */
 
+declare(strict_types=1);
+
 namespace FSi\Bundle\DataSourceBundle\DependencyInjection\Compiler;
 
 use FSi\Bundle\DataSourceBundle\DataSourceBundle;
@@ -14,7 +16,7 @@
 use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 
-class TemplatePathPass implements CompilerPassInterface
+final class TemplatePathPass implements CompilerPassInterface
 {
     public function process(ContainerBuilder $container)
     {
diff --git a/DependencyInjection/Configuration.php b/DependencyInjection/Configuration.php
index 65f86a9..890babb 100644
--- a/DependencyInjection/Configuration.php
+++ b/DependencyInjection/Configuration.php
@@ -7,6 +7,8 @@
  * file that was distributed with this source code.
  */
 
+declare(strict_types=1);
+
 namespace FSi\Bundle\DataSourceBundle\DependencyInjection;
 
 use Symfony\Component\Config\Definition\Builder\TreeBuilder;
diff --git a/DependencyInjection/FSIDataSourceExtension.php b/DependencyInjection/FSIDataSourceExtension.php
index 205e55f..7b3cb9d 100644
--- a/DependencyInjection/FSIDataSourceExtension.php
+++ b/DependencyInjection/FSIDataSourceExtension.php
@@ -7,11 +7,12 @@
  * file that was distributed with this source code.
  */
 
+declare(strict_types=1);
+
 namespace FSi\Bundle\DataSourceBundle\DependencyInjection;
 
-use FSi\Bundle\DataSourceBundle\DataSource\Extension\Symfony\DependencyInjection\Driver\Collection\EventSubscriberInterface;
-use FSi\Bundle\DataSourceBundle\DataSource\Extension\Symfony\DependencyInjection\Driver\Collection\FieldEventSubscriberInterface;
-use FSi\Bundle\DataSourceBundle\DataSource\Extension\Symfony\DependencyInjection\Driver\Doctrine\DBAL\EventSubscriberInterface;
+use FSi\Bundle\DataSourceBundle\DataSource\Extension\Symfony\DependencyInjection\Driver\Collection;
+use FSi\Bundle\DataSourceBundle\DataSource\Extension\Symfony\DependencyInjection\Driver\Doctrine\DBAL;
 use FSi\Bundle\DataSourceBundle\DataSource\Extension\Symfony\DependencyInjection\Driver\Doctrine\ORM;
 use FSi\Component\DataSource\Driver\Collection\CollectionAbstractField;
 use FSi\Component\DataSource\Driver\Doctrine\DBAL\DBALAbstractField;
@@ -66,10 +67,10 @@ private function registerForAutoconfiguration(ContainerBuilder $container): void
         $container->registerForAutoconfiguration(DriverFactoryInterface::class)->addTag('datasource.driver.factory');
         $container->registerForAutoconfiguration(DriverExtensionInterface::class)->addTag('datasource.driver.extension');
         $container->registerForAutoconfiguration(CollectionAbstractField::class)->addTag('datasource.driver.collection.field');
-        $container->registerForAutoconfiguration(FieldEventSubscriberInterface::class)
+        $container->registerForAutoconfiguration(Collection\FieldEventSubscriberInterface::class)
             ->addTag('datasource.driver.collection.field.subscriber')
         ;
-        $container->registerForAutoconfiguration(EventSubscriberInterface::class)
+        $container->registerForAutoconfiguration(Collection\EventSubscriberInterface::class)
             ->addTag('datasource.driver.collection.subscriber')
         ;
         $container->registerForAutoconfiguration(DoctrineAbstractField::class)