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Symfony 5: The Fast Track

A new book to learn about developing modern Symfony 5 applications.

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You are browsing the Symfony 4.3 documentation, which changes significantly from Symfony 3.x. If your app doesn't use Symfony 4.3 yet, browse the Symfony 3.4 documentation.

The Debug Component

4.3 version

The Debug Component

The Debug component provides tools to ease debugging PHP code.

Installation

1
$ composer require symfony/debug

Note

If you install this component outside of a Symfony application, you must require the vendor/autoload.php file in your code to enable the class autoloading mechanism provided by Composer. Read this article for more details.

Usage

The Debug component provides several tools to help you debug PHP code. Enable all of them by calling this method:

use Symfony\Component\Debug\Debug;

Debug::enable();

The enable() method registers an error handler, an exception handler and a special class loader.

Read the following sections for more information about the different available tools.

Caution

You should never enable the debug tools, except for the error handler, in a production environment as they might disclose sensitive information to the user.

Enabling the Error Handler

The ErrorHandler class catches PHP errors and converts them to exceptions (of class ErrorException or FatalErrorException for PHP fatal errors):

use Symfony\Component\Debug\ErrorHandler;

ErrorHandler::register();

This error handler is enabled by default in the production environment when the application uses the FrameworkBundle because it generates better error logs.

Enabling the Exception Handler

The ExceptionHandler class catches uncaught PHP exceptions and converts them to a nice PHP response. It is useful in debug mode to replace the default PHP/Xdebug output with something prettier and more useful:

use Symfony\Component\Debug\ExceptionHandler;

ExceptionHandler::register();

Note

If the HttpFoundation component is available, the handler uses a Symfony Response object; if not, it falls back to a regular PHP response.

Debugging a Class Loader

The DebugClassLoader attempts to throw more helpful exceptions when a class isn't found by the registered autoloaders. All autoloaders that implement a findFile() method are replaced with a DebugClassLoader wrapper.

Using the DebugClassLoader is done by calling its static enable() method:

use Symfony\Component\Debug\DebugClassLoader;

DebugClassLoader::enable();

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.