PHP interceptor example code analysis

class intercept_demo{
    private $xingming = "";
    private $age = 10;
   
    // 若访问一个未定义的属性，则将调用get{$property}对应的方法
    function __get($property){
        $method = "get{$property}";
        if (method_exists($this, $method)){
            return $this->$method();
        }
    }
    // 若给一个未定义的属性设置值，则将调用set{$property}对应的方法
    function __set($property, $value){
        $method = "set{$property}";
        if (method_exists($this, $method)){
            return $this->$method($value);
        }   
    }
   
    // 若用户对未定义的属性调用isset方法，
    function __isset($property){
        $method = "isset{$property}";
        if (method_exists($this, $method)){
            return $this->$method();
        }
    }
   
    // 若用户对未定义的属性调用unset方法，
    // 则认为调用对应的unset{$property}方法
    function __unset($property){
        $method = "unset{$property}";
        if (method_exists($this, $method)){
            return $this->$method();
        }
    }
   
    function __call($method, $arg_array){
        if (substr($method,0,3)=="get"){
            $property = substr($method,3);
            $property = strtolower(substr($property,0,1)).substr($property,1);
            return $this->$property;
        }
    }
   
    function testIsset(){
        return isset($this->Name);
    }
   
    function getName(){
        return $this->xingming;
    }
   
    function setName($value){
        $this->xingming = $value;
    }
   
    function issetName(){
        return !is_null($this->xingming);
    }
   
    function unsetName(){
        $this->xingming = NULL;
    }
}
$intercept = new intercept_demo();
echo "设置属性Name为Li";
$intercept->Name = "Li";
echo "\$intercept->Name={$intercept->Name}";
echo "isset(Name)={$intercept->testIsset()}";
echo "";
echo "清空属性Name值";
unset($intercept->Name);
echo "\$intercept->Name={$intercept->Name}";
echo "";
echo "调用未定义的getAge函数";
echo "age={$intercept->getAge()}";