Wikipedia
Xdebug
Xdebug is a PHP extension which provides debugging and profiling capabilities. It uses the DBGp debugging protocol.
The debug information that Xdebug can provide includes the following:
- stack and function traces in error messages with:
:*full parameter display for user defined functions
:*function name, file name and line indications
:*support for member functions
- memory allocation
- protection for infinite recursions
Xdebug also provides:
- profiling information for PHP scripts
- code coverage analysis
- capabilities to debug your scripts interactively with a debugger front-end.
Xdebug is also available via the PECL.