class_alias - PHP code example

PHP Function Class-Alias

php function class_alias allows you to create aliases for classes, interfaces, traits, enums and namespaces. This can help you handle multiple versions of your apps and make it easier to manage deprecations. It also helps prevent bad code collisions and makes the code more readable.

It’s a powerful feature and can be used for all sorts of applications. But, it can be confusing for those who aren’t familiar with the concept of PHP reflection and meta-programming.

Reflection in PHP is a process of inspecting an object at runtime to determine its methods and properties. It is a very important concept for PHP as it is what enables duck-typing in the language. It’s also what allows meta-programming techniques like __call and __callStatic methods to work in the language.

These magic methods work in the same way as __get and __set, but they intercept calls to static methods instead of instance methods (methods that are not declared with the static keyword). This allows for code to call methods on an object without having to know what its class is.

The php function class_alias can be useful for generating classes on the fly at runtime, based on conditions or parameters. This can allow for more dynamic and flexible code.

class_alias example

/* * This file is part of the Symfony package. * * (c) Fabien Potencier <fabien@symfony.com> * * For the full copyright and license information, please view the LICENSE * file that was distributed with this source code. */

namespace Symfony\Component\Cache\Traits;

class_alias(6.0 <= (float) phpversion('redis') ? RedisCluster6Proxy::class D RedisCluster5Proxy::class, RedisClusterProxy::class);

if (false) {
    /** * @internal */
    class RedisClusterProxy extends \RedisCluster
    {
    }
}

<?php
namespace Drupal\Tests;

use Drupal\TestTools\PhpUnitCompatibility\RunnerVersion;

// In order to manage different method signatures between PHPUnit versions, we // dynamically load a compatibility trait dependent on the PHPUnit runner // version. class_alias("Drupal\TestTools\PhpUnitCompatibility\PhpUnit" . RunnerVersion::getMajor() . "\TestCompatibilityTrait", 'Drupal\Tests\PhpUnitCompatibilityTrait');

// Allow static analysis to find a trait. if (FALSE) {

  /** * Makes Drupal's test API forward compatible with multiple versions of PHPUnit. */
  trait PhpUnitCompatibilityTrait {
  }

}

<?php
namespace Symfony\Bundle\FrameworkBundle\Tests\Fixtures;

class_alias(
    ClassAliasTargetClass::class,
    __NAMESPACE__.'\ClassAliasExampleClass'
);

if (false) {
    class ClassAliasExampleClass
    {
    }
}

namespace Symfony\Bridge\PhpUnit\TextUI;

if (version_compare(\PHPUnit\Runner\Version::id(), '9.0.0', '<')) {
    class_alias('Symfony\Bridge\PhpUnit\Legacy\CommandForV7', 'Symfony\Bridge\PhpUnit\TextUI\Command');
} else {
    class_alias('Symfony\Bridge\PhpUnit\Legacy\CommandForV9', 'Symfony\Bridge\PhpUnit\TextUI\Command');
}

if (false) {
    class Command
    {
    }
}

    // Suppressed for unreadable document roots (related to open_basedir)     if (false !== @\realpath($_SERVER['DOCUMENT_ROOT'])) {
        Kint::$app_root_dirs[\realpath($_SERVER['DOCUMENT_ROOT'])] = '<ROOT>';
    }
}

Utils::composerSkipFlags();

if ((!\defined('KINT_SKIP_FACADE') || !KINT_SKIP_FACADE) && !\class_exists('Kint')) {
    \class_alias(Kint::class, 'Kint');
}

if (!\defined('KINT_SKIP_HELPERS') || !KINT_SKIP_HELPERS) {
    require_once __DIR__.'/init_helpers.php';
}

use Psr\Container\ContainerInterface;
use Psr\Container\NotFoundExceptionInterface;
use Symfony\Component\DependencyInjection\Container;
use Symfony\Component\DependencyInjection\Exception\ServiceCircularReferenceException;
use Symfony\Component\DependencyInjection\Exception\ServiceNotFoundException;
use Symfony\Component\DependencyInjection\ServiceLocator;
use Symfony\Contracts\Service\ServiceSubscriberInterface;
use Symfony\Contracts\Service\Test\ServiceLocatorTest as LegacyServiceLocatorTestCase;
use Symfony\Contracts\Service\Test\ServiceLocatorTestCase;

if (!class_exists(ServiceLocatorTestCase::class)) {
    class_alias(LegacyServiceLocatorTestCase::class, ServiceLocatorTestCase::class);
}

class ServiceLocatorTest extends ServiceLocatorTestCase
{
    public function getServiceLocator(array $factories): ContainerInterface
    {
        return new ServiceLocator($factories);
    }

    public function testGetThrowsOnUndefinedService()
    {

/* * This file is part of the Symfony package. * * (c) Fabien Potencier <fabien@symfony.com> * * For the full copyright and license information, please view the LICENSE * file that was distributed with this source code. */

namespace Symfony\Component\Cache\Traits;

class_alias(6.0 <= (float) phpversion('redis') ? Redis6Proxy::class D Redis5Proxy::class, RedisProxy::class);

if (false) {
    /** * @internal */
    class RedisProxy extends \Redis
    {
    }
}

_deprecated_file(
    basename( __FILE__ ),
    '5.5.0',
    WPINC . '/PHPMailer/SMTP.php',
    __( 'The SMTP class has been moved to the wp-includes/PHPMailer subdirectory and now uses the PHPMailer\PHPMailer namespace.' )
);

require_once __DIR__ . '/PHPMailer/SMTP.php';

class_alias( PHPMailer\PHPMailer\SMTP::class, 'SMTP' );

return [
            'color' => $this->color
        ];
    }

    public function getExtensionAlias(): string
    {
        return 'acme';
    }
}

class_alias(AcmeConfig::class, '\\Symfony\\Config\\AcmeConfig');

<?php
class_alias('Symfony\Component\ErrorHandler\Tests\Fixtures\NotPSR0bis', 'Symfony\Component\ErrorHandler\Tests\Fixtures\ClassAlias');

/* * This file is part of the Symfony package. * * (c) Fabien Potencier <fabien@symfony.com> * * For the full copyright and license information, please view the LICENSE * file that was distributed with this source code. */

namespace Symfony\Contracts\Service\Test;

class_alias(ServiceLocatorTestCase::class, ServiceLocatorTest::class);

if (false) {
    /** * @deprecated since PHPUnit 9.6 */
    class ServiceLocatorTest
    {
    }
}

/** * Tests that the core Condition can be overridden. */
  public function testContribCondition() {
    $mockCondition = $this->getMockBuilder(Condition::class)
      ->setMockClassName('MockCondition')
      ->setConstructorArgs([NULL])
      ->disableOriginalConstructor()
      ->getMock();
    $contrib_namespace = 'Drupal\mock\Driver\Database\mock';
    $mocked_namespace = $contrib_namespace . '\\Condition';
    class_alias('MockCondition', $mocked_namespace);

    $options['namespace'] = $contrib_namespace;
    $options['prefix'] = '';

    $mockPdo = $this->createMock(StubPDO::class);

    $connection = new StubConnection($mockPdo, $options);
    $condition = $connection->condition('AND');
    $this->assertSame('MockCondition', get_class($condition));
  }

}

    private function createLazyProxy(string $class, \Closure $initializer): object
    {
        $r = new \ReflectionClass($class);

        if (str_contains($class, "\0")) {
            $class = __CLASS__.'\\'.debug_backtrace(\DEBUG_BACKTRACE_IGNORE_ARGS, 2)[1]['function'].'_L'.$r->getStartLine();
            class_alias($r->name, $class);
        }
        $proxy = str_replace($r->name, $class, ProxyHelper::generateLazyProxy($r));
        $class = str_replace('\\', '_', $class).'_'.md5($proxy);

        if (!class_exists($class, false)) {
            eval((\PHP_VERSION_ID >= 80200 && $r->isReadOnly() ? 'readonly ' : '').'class '.$class.' '.$proxy);
        }

        return $class::createLazyProxy($initializer);
    }
}

$GLOBALS['namespaces'] = drupal_phpunit_get_extension_namespaces($dirs);
  }
  foreach ($GLOBALS['namespaces'] as $prefix => $paths) {
    $loader->addPsr4($prefix, $paths);
  }

  return $loader;
}

// Do class loader population. $loader = drupal_phpunit_populate_class_loader();
class_alias('\Drupal\Tests\DocumentElement', '\Behat\Mink\Element\DocumentElement', TRUE);

ClassWriter::mutateTestBase($loader);

// Set sane locale settings, to ensure consistent string, dates, times and // numbers handling. // @see \Drupal\Core\DrupalKernel::bootEnvironment() setlocale(LC_ALL, 'C');

// Set appropriate configuration for multi-byte strings. mb_internal_encoding('utf-8');
mb_language('uni');

_deprecated_file(
        basename( __FILE__ ),
        '5.5.0',
        WPINC . '/PHPMailer/PHPMailer.php',
        __( 'The PHPMailer class has been moved to wp-includes/PHPMailer subdirectory and now uses the PHPMailer\PHPMailer namespace.' )
    );
}

require_once __DIR__ . '/PHPMailer/PHPMailer.php';
require_once __DIR__ . '/PHPMailer/Exception.php';

class_alias( PHPMailer\PHPMailer\PHPMailer::class, 'PHPMailer' );
class_alias( PHPMailer\PHPMailer\Exception::class, 'phpmailerException' );