The best solution we've found for debugging/tracing PHP is the Eclipse PDT environment (developed in coordination with Zend) -- Google "Zend PDT" You can use it with either the Zend debugger, or XDebug (which we use). That gives you a nice IDE where you can set breakpoints, view variables, etc. while the script is running.
thank you very much for the most valuable information is it free? could you please explain abit more about debuging php code? the software needed? etc..etc..