6.16 Helpful utility functions: class_exists(), get_class(), and get_declared_classes()This is NOT the latest copy of this book; click here for the latest version.
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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