Debug Drupal 8 Twig Templates with the Twig_Xdebug Module

Debugging Drupal 8 Twig with XDebugWhy use this method

If you're a back end developer who is used to interactive debugging, or a front end developer looking to up your game in Drupal 8, the Twig Xdebug module is for you. Most Drupal developers are used to using dpm() in Drupal 7 and its Drupal 8 counterpart kint(). While this will get you pretty far, using a debugger like Xdebug is a far more powerful. Once installed, you'll be able to quickly inspect all the global and local variables available at a specified breakpoint in the code. You can also step through code to find the functions that created said variable.

 

Requirements/Installation

For many developers, the biggest impediment to using a proper IDE and debugger is the setup. If you're not super comfortable managing your local development environment, taking the time to work through these installations will make you more proficient in the long run.

Xdebug installed on your local server

  • If you use MAMP, Xdebug is installed for you. Just click "Activate Xdebug" on the PHP tab of the MAMP PRO interface.

An Integrated Development Environment (IDE) with XDebug listener enabled.

Xdebug extension for browser

  • Chrome users can use the XDebug helper extension. Just make sure to select your IDE (like PhpStorm) as the IDE key.

Composer installed globally

  • If you use Drush, there's a pretty good chance you already have the Composer package manager installed. Type composer -v in a terminal window to check. If it is not installed, follow the Composer documentation.

Breakpoint Twig Extension PHP library

  • Use the directions in the "INSTALLATION" section of the Twig Xdebug module description page get the PHP library that the module will use. Run the two commands from the root of your Drupal project.

    Watch this video to see what to expect:

Drupal's Twig Xdebug module​​​​​

  • Enable as you would with any other Drupal module.

 

Debug checklist

Now that the hardest part is over, you can set a breakpoint in any twig template. If for some reason it's not working, you'll need to make sure

  1. Your IDE is listening for connections

  2. Your browser extension is set to debug

  3. Xdebug is active (that checkbox in MAMP)

  4. You've set a breakpoint in the twig template with {{breakpoint()}}


Most of the time you'll be looking at the $context variable for values that are available for use in the template.

Here's a video of Twig Xdebug in action:

 

Final Thoughts

Making Xdebug and Twig Xdebug a part of your developer toolset will make you a far more efficient developer. Any time you spend on installation will be worth it later. Though there may be some bumps along the way, Xdebug-related errors are highly Googleable and being able to interactively debug Twig templates is awesome.

Have you tried Twig Xdebug? Are there any tools that help you develop with Drupal 8? Let us know in the comments!