dmorison - 4:18 pm on Jun 18, 2011 (gmt 0)
If you're seeing actual php processes in the top output that would indicate that PHP is running in CGI mode (as opposed to as an Apache module) so instead of "top" try the command "ps ux" (make your terminal window nice and wide!) as this may point to the actual PHP script that has been invoked.
If that is revealing (I'm afraid I'm not in a position to test that immediately) then as a next step run "top" again and note the process IDs of the php instances that appear to be bogging things down, and then pipe the output of "ps ux" through a grep to narrow things down, e.g. if it looks like process ID 2345 is a culprit then use
ps ux | grep 2345