Sometimes there is an issue on your site and you need to resolve it in real time. Here is a method I use to step through code so only I see the debug code/breakpoints. Here is a typical breakpoint:
Code:
if ($_SERVER['REMOTE_ADDR'] == '123.123.123.123') { echo "break"; exit; }
Of course, you need to change the IP address.
I use this method to test configurations or enable settings for just myself. For example, Vbulletin has a debug mode and if I need to debug the live site, I put this at the end of the config file:
Code:
if ($_SERVER['REMOTE_ADDR'] == '123.123.123.123') { $config['Misc']['debug'] = true; }