PHP with XDebug

Xdebug is an extension for PHP and provides a range of features to improve PHP development. It provides step debugging, tracking, profiling, code coverage, and some error reporting improvements.

For this course, however, we’ll be focusing on the step debugging part.

Initially, when one learns PHP for debugging, they usually start out with functions like var_dump, print_r, and var_export in order to figure out the values of certain variables. This approach works when the variables are limited, but when you’re coding on large projects and dealing with a lot of third-party codebase, it becomes time-consuming and does not always help as you need to keep moving these statements from one part of the code to another, trying to figure out where the values are changing. Also, one must remember to remove such statements from code before committing code to the Git repo. That’s where the step debugging part of Xdebug comes in handy.

For a given project, you will have to set it up once, but later, it saves a lot of time when it comes to debugging or analysing the state of any variable or constant at a given breakpoint.

Installing Xdebug:

In order to get started, you need to first install the Xdebug extension, then enable it in the php.ini file. After that, you’ll need to have an IDE that is listening for debug sessions on port 9003 (port 9000 for versions of Xdebug prior to 3) by default. Then, in the browser, you’ll need to install an extension named Xdebug Helper that will allow your requests to have the necessary headers that allow the PHP process to identify which requests to debug (when using the trigger mode for debugging). Later, when PHP requests have the necessary headers, it triggers the PHP process to create a debugger connection with the IDE on the specified port, and at that point, the IDE passes on the breakpoint information to the Xdebug debugger in the PHP process for the request. When the line with the breakpoint is reached, the execution is paused until resumed from the IDE (or you can continue execution line by line using step debugging).

Depending upon which development tools you are using, here are several screencasts showing how to configure Xdebug to debug PHP scripts on WordPress sites:

Video Content	Time
1. PHPStorm with Lando	04:38
2. VSCode with Lando	05:04
3. VSCode with Local by Flywheel	06:22
4. PHPStorm with Local by Flywheel	05:24