On the JetBrains site there's a recent post showing you how to use just-in-time debugging and breakpoints in their PHPStorm IDE combined with the popular PHP debugging tool Xdebug.

In every project comes a moment where code stabilizes and we don’t want to keep the debugger attached to our code all the time. Or maybe we just want to run our code and only attach the debugger when an error occurs or an exception is thrown. Meet Xdebug’s just-in-time (jit) mode and PHP Exception Breakpoints in PhpStorm!

This feature makes use of the "jit" setting for the "remote_mode" setting that Xdebug offers to only send debugging information back to the remote debugger with an error occurs. They show you how to set up PHPStorm for these debugger connections and some example screenshots of it in action. The breakpoints feature compliments this functionality by allowing you to set breakpoints on which kind of errors you want to see information about (ex. warning, notice or deprecated issues).