Helpful utility functions

bool class_exists ( string class_name)

bool get_class ( object object)

array get_declared_classes ( void )

There are three particular OOP-related functions that will make your life easier, and these are class_exists(), get_class(), and get_declared_classes(). In order, class_exists() returns true if the specified class has been declared, get_class() returns the class name of the object you pass to it, and get_declared_classes() returns an array of all classes that you can currently create an object of.

Here are some examples:

<?php

      if ($foo == $bar) {

          $sam = new employee;

      } else {

          $sam = new dog;

      }

  

      print "Sam is a " . get_class($sam) . "\n";

      print "Class animal exists: " . class_exists("animal") . "\n\n\n\n";

      print "All declared classes are: " . get_declared_classes() . "\n";
 ?>

As you can see, the most common use for get_class() is when one object can be of several possible types, as in the code above. C++ users will be familiar with the concept of Runtime Type Information (RTTI), and this is pretty much the same thing.

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