These instructions are for Mac OS X (actually tested on version 10.9.2 Mavericks) with installed MAMP Application (actually tested on MAMP version 3.0.4).
/Applications/MAMP/conf/<selected php version>/
(NOTE: <selected php version> is the php version that you have selected in the MAMP configuration)
[xdebug] ;zend_extension="/Applications/MAMP/bin/php/<selected php version>/lib/php/extensions/no-debug-non-zts-20121212/xdebug.so"
by removing the ; character at the beginning of the line
xdebug.remote_enable=on xdebug.remote_handler=dbgp xdebug.remote_host=localhost xdebug.remote_port=9000
Note: You can set a different port number if you need.