The Debug Component
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Read the updated version of this page for Symfony 7.1 (the current stable version).
The Debug component provides tools to ease debugging PHP code.
2.3
The Debug component was introduced in Symfony 2.3. Previously, the classes were located in the HttpKernel component.
Installation
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$ composer require symfony/debugAlternatively, you can clone the https://github.com/symfony/debug repository.
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. Enabling them all is as easy as it can get:
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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 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):
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use Symfony\Component\Debug\ErrorHandler;
ErrorHandler::register();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:
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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 as easy as calling its static
enable() method:
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use Symfony\Component\Debug\DebugClassLoader;
DebugClassLoader::enable();