Just make sure you have php-xdebug installed and edit your php.ini:
[xdebug]
xdebug.profiler_enable = 0
xdebug.profiler_enable_trigger = 1
xdebug.profiler_output_dir = "/tmp/xdebug/"
xdebug.output_name = "cachegrind.out.%t-%s"
Also make and set permissions on /tmp/xdebug:
mkdir /tmp/xdebug
chmod 777 /tmp/xdebug
After that simply load the output files into "kcachegrind" on your Desktop.
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