php - __call() 方法说明

Question

我有这部分代码:

class FTPClient
{
    public function __construct() {
        $args_num=func_num_args();
        echo $args_num;
        $this->{"__construct".($args_num===0 ? '' : $args_num)}(func_get_args());
    }

    function __call($name,$args) {
        echo $name,count($args),'<br/>';
    }

    public function open() {
        echo 'open';
    }
}
    $o = new FTPClient('127.0.0.1','user','pass');
    $o = new FTPClient();
    $o = new FTPClient('127.0.0.1','user');
    $o->close();

输出如下所示:

3__construct3101__construct11 //Don't understand how this output came together?!2__construct21close0

有人可以帮我解释一下这个输出的第二行吗？

Answer 1

1. 第一个示例

   $o = new FTPClient('127.0.0.1','user','pass');

   You have 3 arguments, means 3 gets printed with this line:

   $args_num = func_num_args();echo $args_num;  //output: 3

   After that you are trying to call the method __construct3():

   $this->__construct3(func_get_args());

   Which is not accessible, means __call() gets called. In that magic method you print the name, here __construct3 and the count of the arguments, here the argument array, means 1.

   Output:

   3__construct31
   

2. 第二个示例

   $o = new FTPClient();

   You have 0 arguments, means 0 gets printed with this line:

   $args_num = func_num_args();echo $args_num;  //output: 0

   After that you are trying to call the method __construct(), the constructor:

   $this->__construct(func_get_args());

   And the constructor is callable, so __call() won't get called here. Instead the constructor gets called again, but with an array, which holds the array of arguments, here an empty array.

   Now in the second call you have 1 argument, means 1 gets printed with this line:

   $args_num = func_num_args();echo $args_num;  //output: 1

   After that you are trying to call the method __construct1():

   $this->__construct1(func_get_args());

   Now __construct1() is not accessible, means __call() gets triggered. In that magic method you print the name, here __construct1 and the count of the arguments, here an array with the argument array, means 1.

   Output:

   01__construct11
   

注释:

• __call()当您尝试调用无法访问的方法时会被触发。