zend_extension="/usr/local/lib/php/extensions/no-debug-non-zts-20060613/xdebug.so
[XDebug]
xdebug.profiler_append = 1
xdebug.profiler_enable = 0 (I've tried this both on and off)
xdebug.profiler_enable_trigger = 1
xdebug.profiler_output_dir = "/debug/xdebug/profiler_output_dir"
xdebug.profiler_output_name = "cachegrind.out.%p"

http://mydomain.com/my_page.php?XDEBUG_PROFILE
-or-
http://mydomain.com/my_page.php?XDEBUG_PROFILE=1

xdebug.profiler_append=1
xdebug.profiler_output_dir ="/home/username/debug/xdebug/profiler_output_dir"
xdebug.profiler_output_name = "cachegrind.out.%s.%H"

sudo chmod go+w /home/dimitris/cachegrind/