On the Developer Tutorials blog today, Hasin Hayder has pointed out a handy PHP function that can make your debugging a bit less of a headache - debug_backtrace.
Most of the PHP developers debug php code in their local machine just by trial and error using "print_r","var_dump" and "echo". They don't write unit tests or follow any advanced debugger like xdebug. But the problem of using these methods is you cannot fool proof your code and their might be some bugs still present in your code.
He includes a simple example to show how it works and what kind of output it will give - a nested function call. Personally, I use this in some of my classes (like a database abstraction later) to track and see which functions my calls are coming from and what data they're sending me - easier to debug in one place than trying to guess.