Examples

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, 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 Class Definitions

Vegetable


<?php

class Vegetable {
    public $edible;

    public $color;

    public function __construct($edible, $color = "green")
    {
        $this->edible = $edible;
        $this->color = $color;
    }

    public function isEdible()
    {
        return $this->edible;
    }

    public function getColor()
    {
        return $this->color;
    }
}

?>

Spinach


<?php

class Spinach extends Vegetable {
    public $cooked = false;

    public function __construct()
    {
        parent::__construct(true, "green");
    }

    public function cook()
    {
        $this->cooked = true;
    }

    public function isCooked()
    {
        return $this->cooked;
    }
}

?>

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


<?php

// register autoloader to load classes
spl_autoload_register();

function printProperties($obj)
{
    foreach (get_object_vars($obj) as $prop => $val) {
        echo "\t$prop = $val\n";
    }
}

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

function objectBelongsTo($obj, $class)
{
    if (is_subclass_of($obj, $class)) {
        echo "Object belongs to class " . get_class($obj);
        echo ", a subclass of $class\n";
    } else {
        echo "Object 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";
printProperties($veggie);

// and leafy methods
echo "\nleafy: Methods\n";
printMethods($leafy);

echo "\nParentage:\n";
objectBelongsTo($leafy, Spinach::class);
objectBelongsTo($leafy, Vegetable::class);

?>

The above examples will output:

veggie: CLASS Vegetable
leafy: CLASS Spinach, PARENT Vegetable

veggie: Properties
        edible = 1
        color = blue

leafy: Methods
        function __construct()
        function cook()
        function isCooked()
        function isEdible()
        function getColor()

Parentage:
Object does not belong to a subclass of Spinach
Object belongs to class Spinach, a subclass of 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.