Use MacGDBp Debugger
In order to use the MacGDBp Debugger you first must enable the Xbedug extension on the PHP tab. Restart your servers in MAMP PRO. Open the MacGDBp Debugger application. You may see a warning message relating to incoming network connections, press ‘Allow’ to proceed.
Open your host site and you should see an empty page in your browser. This is because the MacGDBp debugger has stopped your code at the first line of PHP code. You can now step through your PHP code.