xdebug

When you need to get to the bottom of a PHP error that's jumping out of your Drupal pages, there there is no better tool to use than XDebug.

X-Debug lets developers see all of the values that are getting plugged into a web page, as it's being compiled and run on the Apache server that's running Drupal, and step line by line through a text editor such ass Atom or Komodo ActiveState.

If your Drupal themers or WordPress developers aren't using X-Debug to find the problems in their applications then your spending too much cash on their time in troubleshooting develpment hurdles.