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Class/Object Functions

VIII. Class/Object Functions



These functions allow you to obtain information about classes and instance objects. You can obtain the name of the class to which a object belongs, as well as its member properties and methods. Using these functions, you can find out not only the class membership of an object, but also its parentage (i.e. what class is the object class extending).

An example of use

In this example, we first define a base class and an extension of the class. The base class describes a general vegetable, whether it is edible or not and what is its color. The subclass Spinach adds a method to cook it and another to find out if it is cooked.

Example 1.


// base class with member properties and methods
class Vegetable {

	var $edible;
	var $color;

	function Vegetable( $edible, $color="green" ) {
		$this->edible = $edible;
		$this->color = $color;

	function is_edible() {
		return $this->edible;

	function what_color() {
		return $this->color;
} // end of class Vegetable

// extends the base class
class Spinach extends Vegetable {

	var $cooked = false;

	function Spinach() {
		$this->Vegetable( true, "green" );

	function cook_it() {
		$this->cooked = true;

	function is_cooked() {
		return $this->cooked;
} // end of class Spinach


We then instantiate 2 objects from these classes and print out information about them, including their class parentage. We also define some utility functions, mainly to have a nice printout of the variables.

Example 2. test_script.php


include "";

// utility functions

function print_vars($obj) {
	$arr = get_object_vars($obj);
	while (list($prop, $val) = each($arr))
		echo "\t$prop = $val\n";

function print_methods($obj) {
	$arr = get_class_methods(get_class($obj));
	foreach ($arr as $method)
		echo "\tfunction $method()\n";

function class_parentage($obj, $class) {
	global $$obj;
	if (is_subclass_of($$obj, $class)) {
		echo "Object $obj belongs to class ".get_class($$obj);
		echo " a subclass of $class\n";
	} else {
		echo "Object $obj does not belong to a subclass of $class\n";

// instantiate 2 objects

$veggie = new Vegetable(true,"blue");
$leafy = new Spinach();

// print out information about objects
echo "veggie: CLASS ".get_class($veggie)."\n";
echo "leafy: CLASS ".get_class($leafy);
echo ", PARENT ".get_parent_class($leafy)."\n";

// show veggie properties
echo "\nveggie: Properties\n";

// and leafy methods
echo "\nleafy: Methods\n";

echo "\nParentage:\n";
class_parentage("leafy", "Spinach");
class_parentage("leafy", "Vegetable");

One important thing to note in the example above is that the object $leafy is an instance of the class Spinach which is a subclass of Vegetable, therefore the last part of the script above will output:

Object leafy does not belong to a subclass of Spinach
Object leafy belongs to class spinach a subclass of Vegetable

Table of Contents
get_class — Returns the name of the class of an object
get_parent_class — Returns the name of the parent class of an object
get_class_methods — Returns an array of class methods' names
get_class_vars — Returns an array of default properties of the class
get_object_vars — Returns an associative array of object properties
is_subclass_of — Determines if an object belongs to a subclass of the specified class
class_exists — Checks if the class has been defined
method_exists — Checks if the class method exists
get_declared_classes — Returns an array with the name of the defined classes
call_user_method — Call a user method on an specific object

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