Type Operators instanceof is used to determine whether a PHP variable is an instantiated object of a certain class/a class that implements an interface
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0-instanceof is used to determine whether a PHP variable is an instantiated object of a certain class
1-instanceof can also be used to determine whether a variable is an instantiated object of a class that inherits from a parent class
2-Lastly, instanceof can also be used to determine whether a variable is an instantiated object of a class that implements an interface
http://php.net/manual/en/language.operators.type.php
http://php.net/manual/zh/language.operators.type.php
类型运算符
instanceof 用于确定一个 PHP 变量是否属于某一类 class 的实例
instanceof 也可用来确定一个变量是不是继承自某一父类的子类的实例
最后,instanceof也可用于确定一个变量是不是实现了某个接口的对象的实例
<?php interface MyInterface { } class MyClass implements MyInterface { } $a = new MyClass; var_dump($a instanceof MyClass); var_dump($a instanceof MyInterface);
bool(true) bool(true)
<?php interface MyInterface { } class MyClass implements MyInterface { } $a = new MyClass; $b = new MyClass; $c = 'MyClass'; $d = 'NotMyClass'; var_dump($a instanceof $b); // $b is an object of class MyClass var_dump($a instanceof $c); // $c is a string 'MyClass' var_dump($a instanceof $d); // $d is a string 'NotMyClass'
bool(true) bool(true) bool(false)
instanceof does not throw any error if the variable being tested is not an object, it simply returns FALSE
. Constants, however, are not allowed.
如果被检测的变量不是对象,instanceof 并不发出任何错误信息而是返回 FALSE
。不允许用来检测常量。
<?php $a = 1; $b = NULL; $c = imagecreate(5, 5); var_dump($a instanceof stdClass); // $a is an integer var_dump($b instanceof stdClass); // $b is NULL var_dump($c instanceof stdClass); // $c is a resource var_dump(FALSE instanceof stdClass);
bool(false) bool(false) bool(false)