When you are working on a web site or web application, something that little thought is spared for at development time all too often is it’s performance. You need to know where your bottlenecks are and what the costs of each architectural and implementation choice you make are. You should routinely profile your application’s core functions to see how they behave. How do we do this? You could put little timers into the code and log timings to see how things work, or you could use XDebug.

XDebug is a PHP extension that provides a number of critical features to developers. It supports step through debugging (assuming your code editor can hook into it) and it supports profiling of your scripts. This gives you a detailed breakdown of every command executed in your application, how many times it was executed and what it cost.

This is invaluable when tracing your performance work. You can identify exactly which routines are costing you too much. It can give valuable insight into the performance landscape of your software. So I’m going to hook it up into my development environment on it’s USB key.

Firstly, pop over to the XDebug site and download the relevant version for your PHP version. I downloaded the Windows Binary of 2.0RC4 for PHP 5.2.1+. XDebug is a “Zend Extension”, it’s not a standard PHP Extension, it extends the Zend Engine that powers PHP. This changes how we configure it in php.ini and means it doesn’t have to go on the extensions folder of your PHP install. But, I keep it there for consistency. Once placed in that file you need to edit your php.ini, the commands can go anywhere in the file, but, I placed them after the PHP Extension loading commands, again for consistency:

zend_extension_ts=/development/php/ext/php_xdebug-2.0.0rc4-5.2.1.dll

Note that this is loaded with the zend_extension_ts command instead of the extension command (the ts denotes Thread Safe mode) . Also note that we specify the full path to the extension. The zend_extension_ts (and other zend_extension commands) need the full path as they don’t pay attention to our extension directory command.

Once this is done, go to your PHPInfo() test page and check, you should have XDebug information included:

Ok so far so good. If you have a page which currently throws a php error, go check it now. You’ll notice that just having XDebug installed gives you much more information. XDebug makes developing easier just by being there.

Now, we’re mainly going to use it to profile performance of our applications and third party libraries, so we need to enable profiling, this is done with a couple of new entries in php.ini. I placed them just after my command to load the extension so it’s all in one place:

xdebug.profiler_enable = 1
xdebug.profiler_output_dir=/development/

Now restart Apache and hit your PHPInfo() page. In the development folder on your USB Key you will have some files called cachegrind.out.[some number]. This is the profiling information in it’s raw form and of no use to you on it’s own.

You need a cachegrind analysis program. I use Wincachegrind as I’m on windows. You can use this to open up the cachegrind file and see what took what time. Visit yourPHPInfo() page, pick up the cachegrind output and take a look. You can see a lot of detail.

I don’t propose to detail how to use Wincachegrind and do a full analysis, a bit of poking should show you what’s going on. But, I’ll be using XDebug and WinCacheGrind to get under the covers of some third party libraries I’m considering for use in the development of Multiblog, so we’ll see more information then.

Popularity: 62% [?]

This is version 2 of this entry and was posted 1 year, 3 months ago on Saturday, June 23rd, 2007 at 7:49 am and is filed under PHP, Portable Development. It's popularity ranking is Popularity: 62% [?]. It has been tagged with performance, PHP, portable, portabledevelopment, wincachegrind, xdebug. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site. You can see changes since the last version here.