php5-xdebug: How to Profile a PHP application

This packets permits to get a trace of all the calls in a PHP scripts with the relative execution times. These information are extremely useful to optimize the code and to find unexpected behaviours.

To get it you need to execute (on Debian/Ubuntu)

aptitude install php5-xdebug

The minimal configuration to activate it is

zend_extension=/usr/lib/php5/20090626/xdebug.so
xdebug.profiler_enable=1
xdebug.profiler_output_dir=/tmp

After that you’ll find the result of the trace of the execution in the /tmp directory in files named

cachegrind.out.

These files are extremely difficult to reed so it is mandatory tu use some graphic tools to access them. A good one is kcachegrind.

This library, can overload the server, so it is a good practice to remove it when it isn’t needed.