The internal debugger in PHP 3 is useful for tracking down evasive bugs. The debugger works by connecting to a TCP port for every time PHP 3 starts up. All error messages from that request will be sent to this TCP connection. This information is intended for "debugging server" that can run inside an IDE or programmable editor (such as Emacs).
How to set up the debugger:
hostis the IP number or name of the host running the TCP listener.
Now, all warnings, notices etc. will show up on that listener socket, even if you turned them off with error_reporting().