PHP magic methods: __isset and __unset

From php5 and later versions, classes can use magic methods. PHP stipulates that methods starting with two underscores (__) are reserved as magic methods, so it is recommended that function names do not start with __ unless it is to overload existing magic methods.

The existing magic methods in PHP include __construct, __destruct, __call, __get, __set, __isset, __unset, __sleep, __wakeup, __toString, __set_state and __clone.

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__isset() - When using the isset() method on a class attribute or a non-class attribute, if there is no or non-public attribute, the __isset() method will be automatically executed.

__unset()　-When using the unset() method on a class attribute or a non-class attribute, if there is no or non-public attribute, the __unset() method will be automatically executed

<?php
    /**
     * 针对类中的魔术方法 __isset() 和 __unset() 的例子
     */

class Example {
    public $public;
    protected $protected;
    private $private;
    
    public function __construct(){
        $this->public = 'pub';
        $this->protected = 'pro';
        $this->private = 'pri';
    }
    
    public function __isset($var){
        echo '这里通过__isset()方法查看属性名为 '.$var."\n";
    }
    
    public function __unset($var){
        echo '这里通过__unset()方法要销毁属性名为 '.$var."\n";
    }
}

$exa = new Example;

echo '<pre class="brush:php;toolbar:false">';
var_dump(isset($exa->public));
echo "\n";
var_dump(isset($exa->protected));
echo "\n";
var_dump(isset($exa->private));
echo "\n";
var_dump(isset($exa->noVar));
echo "\n";
echo '<hr/>';


unset($exa->public);
var_dump($exa);

echo "\n";
unset($exa->protected);
echo "\n";
unset($exa->private);
echo "\n";
unset($exa->noVar);
echo "\n";

The result is as follows:

bool(<span>true</span><span>)

这里通过__isset()方法查看属性名为 protected
bool(</span><span>false</span><span>)

这里通过__isset()方法查看属性名为 private
bool(</span><span>false</span><span>)

这里通过__isset()方法查看属性名为 noVar
bool(</span><span>false</span><span>)
------------------------------------------------------------------------------ </span><span>object</span>(Example)#<span>1</span> (<span>2</span><span>) {
  [</span><span>"</span><span>protected:protected"]=></span> <span>string</span>(<span>3</span>) <span>"</span><span>pro"</span> [<span>"</span><span>private:private"]=></span> <span>string</span>(<span>3</span>) <span>"</span><span>pri"</span> <span>}

这里通过__unset()方法要销毁属性名为 protected

这里通过__unset()方法要销毁属性名为 private

这里通过__unset()方法要销毁属性名为 noVar</span>

​

The above introduces the PHP magic methods: __isset and __unset, including the content of PHP magic methods. I hope it will be helpful to friends who are interested in PHP tutorials.