Scenario:
You need to debug an existing PHP site (wordpress, joomla, drupal, etc..), and you find it very difficult/time-consuming to set up your development IDE to simulate the deployed environment.
You want to have a quick look of what's actually going on, directly from the SSH terminal.
TL;DR
Use xdebug to intercept PHP scripts, and communicate with vdebug via dbgp.
(Please ignore the rest of article if you are not comfortable with vim - the editor).
Read more How to Remotely Debug PHP
Using Terminal (Vim + VDebug + XDebug)