在这个示例中，首先定义了一个基类和该类的扩展。基类描述了普通的蔬菜， 是否可食用及其颜色。子类 Spinach 添加了烹饪的方法和检查是否已烹饪的方法。
示例 #1 定义类
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 $this->cooked;
}
}
?>接下来从这些类中实例化了两个对象并打印了它们的信息，包括了他们类的继承关系。 同时也定义了一些实用函数，主要为了漂亮地打印出这些变量。
示例 #2 test_script.php
<?php
// 注册自动加载器以加载类
spl_autoload_register();
function printProperties($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";
}
}
// 实例化 2 对象
$veggie = new Vegetable(true, "blue");
$leafy = new Spinach();
// 打印这些对象的信息
echo "veggie: CLASS " . get_class($veggie) . "\n";
echo "leafy: CLASS " . get_class($leafy);
echo ", PARENT " . get_parent_class($leafy) . "\n";
// 显示蔬菜的属性
echo "\nveggie: Properties\n";
printProperties($veggie);
// 和 leafy 的方法
echo "\nleafy: Methods\n";
printMethods($leafy);
echo "\nParentage:\n";
objectBelongsTo($leafy, Spinach::class);
objectBelongsTo($leafy, Vegetable::class);
?>以上示例会输出：
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
一个重要的事情是需要注意在上面的示例中，对象 $leafy 是 Spinach 的实例（Vegetable 的子类）。