title: measuring php performance
body: <p>I'm trying to track down issues with an application [modx] I have several of these sites [about 10] on my server &amp; was wondering how I can see what php is doing. </p>
  
  <p>Pages on these sites are extremely slow while the same sites in dev are fine as are other php applications on the server. </p>
  
  <p>I tried using xdebug to get an idea of what php was doing while processing these pages &amp; where the bottleneck was occurring, but it only appeared to want to do anything on an error [there are no errors being thrown] </p>
  
  <p>Any suggestions on how to track this down?
  [linux/Centos5/php5.2.?/apache2] </p>