Anything involving Eclipse is always epic. First, you have to get your head around what distribution of it to use, as confusing as one's first introduction to Linux distributions (there are different kinds of Linux?).

Next, you have to grok the fact that the Zend Debugger must be installed on your server. In this case, MAMP.

Then, you have to make Eclipse listen to the debugging information being outputted, on the debug port.

Finally, you have to figure out how to use a debugger effectively (not in scope, but careful, debugging will blow your mind).