quick start Linux + PHP + XDebug howto

Ever really debugged before? It’s a life changer. Forget dpm, dd, print_r, var_dump…

1) Install a debugger of your choice (NetBeans, protoeditor, Komodo, Eclipse…)

2) Install/Configure XDebug extension

pecl install xdebug

If you get errors regarding pecl, phpize or missing libraries, try installing the php-pecl and php-devel packages.

Go to /etc/php.d, or wherever your PHP configuration files live. If you see “xdebug.ini” move it to “00xdebug.ini”. THIS IS THE MOST IMPORTANT PART. We have to rename it because XDebug has to run before all other extensions. If you have other extensions like datacache, other debuggers (Zend), or optimizers, you should disable them. Otherwise, XDebug will show as loaded but it won’t work.

Edit 00xdebug.ini and put the following code in:

xdebug.idekey=netbeans-xdebug ;change to same ide key in your debugger

3) Check configuration
Check the output of “php -i” and paste it into http://xdebug.org/find-binary.php. It will yell at you if you did anything wrong.

4) Install the XDebug helper for Firefox or Chrome
This allows you to toggle debugging on and off for local sites.

Figure out how to enable debugging in the debugger of your choice and set a break point at a function call. Open up the page in your browser and make sure you use the XDebug helper to set debugging on. Your debugger should halt at the line. Now you can see all your local variables and dive into function calls.

XDebug also profiles. Making a web request with ?XDEBUG_PROFILE=1 in the URL will enable the profile and dump to xdebug.profiler_output_dir. You can take these dumps and use a program like cachegrind to analyze the request.

I use Fedora on a daily basis to debug using Zend Server as my stack, but this will also work on any other configuration (Debian, Mac) – just change the paths to what they are on your system.