1.) install “Xdebug”: (http://www.xdebug.org/docs/profiler)

sudo apt-get install php5-xdebug

2.) configure “Xdebug”:

xdebug.profiler_enable_trigger = 1
xdebug.profiler_output_dir = “/tmp”
xdebug.profiler_output_name = “cachegrind.out.%t-%s”
xdebug.remote_enable = 1
xdebug.remote_handler = “dbgp”
xdebug.remote_host = “127.0.0.1”
xdebug.trace_output_dir = “/tmp”
xdebug.remote_port=9000

3.)

send “XDEBUG_PROFILE=1″ via _GET or _POST

4.) use e.g. “QCacheGrind”, “WinCacheGrind” or “KCachegrind” (http://kcachegrind.sourceforge.net/html/Home.html) to visualize the results

PS: and there is also a memory usage profiler for the “Cachegrind”-Tools -> “memprof”(https://github.com/arnaud-lb/php-memory-profiler), but in the most cases XDebug will help you 🙂