If you develop website using some framework (Symfony, Codeigniter or Zend etc), you need to play with several system defined objects like routing objects, session objects etc. To see what are the functions available inside an object on run time without referring the parent class documentation, here is a trick:

printr( getclassmethods(getclass($YourObject)));

Now you can try each functions. This will save a lot of your time without going to the definition.

I use this method, when I develop using symfony to explore an object, eg: $this->getRequest() , to know what are the other functions I can call using this getRequest()

Keep it simple !