Whenever an exception occurs PHP outputs the file+line number, which caused the error:

Fatal error: Uncaught exception 'Exception' with message 'Value must be 1 or below' in C:\webfolder\test.php:6
Stack trace: #0 C:\webfolder\test.php(12): checkNum(2 #1 {main} thrown in C:\webfolder\test.php on line 6

What about register phped as an url protocol and by clicking on the filename (C:\webfolder\test.php:6) the system would bring up PhpEd, load the file and jump to the given line.

if you break into debugger, you'll see the call-stack in Call Stack window, it's where you can click and check what caused the error