OpenSourcery

Dylan was helping me out with a nasty Drupal problem when I finally decided to seek out a PHP debugger. He told me about Xdebug. It uses a debugging protocol called DBGp. Because of this you can attach a debugger to a suitably enlightened process, for example a Drupal server. Now I loves me some debugger. I've never been a fan of sprinkling print statements around, scrying through logs, realizing you didn't print the right information and rerunning everything, and finally forgetting to remove those same debugging prints. But I've never been able to attach a debugger to a real live running web process. With this, maybe me and Drupal won't fight like two cats in a back alley.

Unfortunately, Dylan runs the debugger with Eclipse. I resigned myself to my fate and began downloading the ONE HUNDRED MEG Eclipse installer. I'm an Emacs user (in an office full of vi folks). Emacs is pretty damn fat, but it has nothing on Eclipse. (Yo editor so fat, it makes Emacs look thin!) While that oozed onto my computer, I did a little searching around for an Emacs widget for Xdebug. Of course there's one: GEBEN.

GEBEN installs like any other Emacs library. Xdebug like any other PHP extension. Once installed you have to add some bits to your php.ini

zend_extension="/usr/local/lib/php5/modules/xdebug.so"
 
xdebug.remote_enable=On
xdebug.remote_autostart=On

Loads the xdebug extension, turns on the debugging and makes it always look for a server. Without xdebug.remote_autostart on you have to shim XDEBUG_SESSION_START=1 into your GETs and POSTs. With that in place, kick over your web server. You can read up on all the config options.

XDebug works by trying to connect to a debugging server on port 9000. GEBEN provides that server. Fire up Emacs and run M-x geben. GEBEN is now listening. The next PHP you run should show up in Emacs.

   <?php
 
=> print("Hello world\n");
 
   ?>

Congratulations, you are now debugging PHP. What now? Now, type M-x geben-mode-help to get the debugger commands. They're pretty primitive. Step over, step into, step out, continue running, set breakpoints. One of the nice commands is v geben-display-context which will show you all the variables in scope, and it will update as you step through the program. e geben-eval-expression is handy to run random bits of code.

Now you can debug any PHP process, any time, in any environment. You can debug running web sites, no more having to mock up a web environment just to get a debugger. Because it's a debugging protocol it can conceivably be bolted onto anything. Activestate has added it to Perl via Komodo. Don't like Emacs? There's a small truckload of clients. This makes me happy.

(Note, there's NO security on this thing. If you're going to use it outside localhost run it through an ssh tunnel.)

Eclipse? I figured all this out before it was even done downloading.