PHP魔术方法__isset()
2018-09-16 19:00 By
"Powerless"
3086
0
1
在对象外部使用isset()方法有两种情况：
如果参数是公有属性，那么可以利用isset()方法判断属性是否被设置；
如果参数是私有属性，isset()方法将无法使用。
那么，是否有办法判断私有属性被设置呢？当然，只需要在类里定义__isset()方法，就可以在对象外部利用isset()方法判断某个私有属性是否被设置了。
对未定义或没有权限访问的属性调用isset()或empty()时，就会调用__isset()方法。
示例代码如下：
<?php
class Person
{
public $sex;
private $name;
private $age;
public function __construct($name="", $age=25, $sex='Male')
{
$this->name = $name;
$this->age = $age;
$this->sex = $sex;
}
/**
* @param $content
*
* @return bool
*/
public function __isset($content) {
echo "The {$content} property is private，the __isset() method is called automatically.<br>";
echo isset($this->$content);
}
}
$person = new Person("John", 25); // 赋初始值
echo isset($person->sex),"<br>";
echo isset($person->name),"<br>";
echo isset($person->age),"<br>";
输出结果如下：
1 The name property is private，the __isset() method is called automatically. 1 The age property is private，the __isset() method is called automatically. 1
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