Symfony
sponsored by SensioLabs
Menu
  • About
  • Documentation
  • Screencasts
  • Cloud
  • Certification
  • Community
  • Businesses
  • News
  • Download
  1. Home
  2. Documentation
  3. Components
  4. The Debug Component
  • Documentation
  • Book
  • Reference
  • Bundles
  • Cloud
Search by Algolia

Table of Contents

  • Installation
  • Usage
  • Enabling the Error Handler
  • Enabling the Exception Handler
  • Debugging a Class Loader

The Debug Component

Edit this page

Warning: You are browsing the documentation for Symfony 4.1, which is no longer maintained.

Read the updated version of this page for Symfony 6.2 (the current stable version).

The Debug Component

The Debug component provides tools to ease debugging PHP code.

Installation

1
$ composer require symfony/debug

Alternatively, 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 can be done by calling the static method Debug::enable():

1
2
3
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):

1
2
3
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:

1
2
3
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.

To activate the DebugClassLoader, call its static enable() method:

1
2
3
use Symfony\Component\Debug\DebugClassLoader;

DebugClassLoader::enable();
This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.
We stand with Ukraine.
Version:
Symfony Code Performance Profiling

Symfony Code Performance Profiling

Be trained by SensioLabs experts (2 to 6 day sessions -- French or English).

Be trained by SensioLabs experts (2 to 6 day sessions -- French or English).

↓ Our footer now uses the colors of the Ukrainian flag because Symfony stands with the people of Ukraine.

Avatar of Tavo Nieves J, a Symfony contributor

Thanks Tavo Nieves J (@tavoniievez) for being a Symfony contributor

6 commits • 264 lines changed

View all contributors that help us make Symfony

Become a Symfony contributor

Be an active part of the community and contribute ideas, code and bug fixes. Both experts and newcomers are welcome.

Learn how to contribute

Symfony™ is a trademark of Symfony SAS. All rights reserved.

  • What is Symfony?
    • Symfony at a Glance
    • Symfony Components
    • Case Studies
    • Symfony Releases
    • Security Policy
    • Logo & Screenshots
    • Trademark & Licenses
    • symfony1 Legacy
  • Learn Symfony
    • Symfony Docs
    • Symfony Book
    • Reference
    • Bundles
    • Best Practices
    • Training
    • eLearning Platform
    • Certification
  • Screencasts
    • Learn Symfony
    • Learn PHP
    • Learn JavaScript
    • Learn Drupal
    • Learn RESTful APIs
  • Community
    • SymfonyConnect
    • Support
    • How to be Involved
    • Code of Conduct
    • Events & Meetups
    • Projects using Symfony
    • Downloads Stats
    • Contributors
    • Backers
  • Blog
    • Events & Meetups
    • A week of symfony
    • Case studies
    • Cloud
    • Community
    • Conferences
    • Diversity
    • Documentation
    • Living on the edge
    • Releases
    • Security Advisories
    • SymfonyInsight
    • Twig
    • SensioLabs
  • Services
    • SensioLabs services
    • Train developers
    • Manage your project quality
    • Improve your project performance
    • Host Symfony projects
    Deployed on
Follow Symfony
Search by Algolia