is_subclass_of

(PHP 4, PHP 5, PHP 7, PHP 8)

is_subclass_of检查对象是否继承或者实现(implement)此类

说明

is_subclass_of(mixed $object_or_class, string $class, bool $allow_string = true): bool

检查指定的 object_or_class 是否继承或者实现(implement) class

参数

object_or_class

类名或者对象实例。如果类不存在,也不会报错。

class

类名

allow_string

如果此参数设置为 false,将不允许将字符串类名传递给 object_or_class。如果类不存在,这也可以防止调用自动加载器。

返回值

如果对象 object_or_class 属于 class 的子类,则返回 true,否则返回 false

示例

示例 #1 is_subclass_of() 示例

<?php
// 定义类
class WidgetFactory
{
var
$oink = 'moo';
}

// 定义子类
class WidgetFactory_Child extends WidgetFactory
{
var
$oink = 'oink';
}

// 创建新对象
$WF = new WidgetFactory();
$WFC = new WidgetFactory_Child();

if (
is_subclass_of($WFC, 'WidgetFactory')) {
echo
"yes, \$WFC is a subclass of WidgetFactory\n";
} else {
echo
"no, \$WFC is not a subclass of WidgetFactory\n";
}


if (
is_subclass_of($WF, 'WidgetFactory')) {
echo
"yes, \$WF is a subclass of WidgetFactory\n";
} else {
echo
"no, \$WF is not a subclass of WidgetFactory\n";
}


if (
is_subclass_of('WidgetFactory_Child', 'WidgetFactory')) {
echo
"yes, WidgetFactory_Child is a subclass of WidgetFactory\n";
} else {
echo
"no, WidgetFactory_Child is not a subclass of WidgetFactory\n";
}
?>

以上示例会输出:

yes, $WFC is a subclass of WidgetFactory
no, $WF is not a subclass of WidgetFactory
yes, WidgetFactory_Child is a subclass of WidgetFactory

示例 #2 is_subclass_of() 使用接口示例

<?php
// 定义接口
interface MyInterface
{
public function
MyFunction();
}

// 定义实现了接口的类
class MyClass implements MyInterface
{
public function
MyFunction()
{
return
"MyClass Implements MyInterface!";
}
}

// 实例化对象
$my_object = new MyClass;

// 自 5.3.7 起可用

// 使用类的对象实例进行检查
if (is_subclass_of($my_object, 'MyInterface')) {
echo
"Yes, \$my_object is a subclass of MyInterface\n";
} else {
echo
"No, \$my_object is not a subclass of MyInterface\n";
}

// 使用字符串类名进行检查
if (is_subclass_of('MyClass', 'MyInterface')) {
echo
"Yes, MyClass is a subclass of MyInterface\n";
} else {
echo
"No, MyClass is not a subclass of MyInterface\n";
}
?>

以上示例会输出:

Yes, $my_object is a subclass of MyInterface
Yes, MyClass is a subclass of MyInterface

注释

注意:

如果此类不是已知类,使用此函数会使用任何已注册的 autoloader

参见

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