callback 语法在PHP中有点奇怪.您需要做的是创建一个数组.第一个元素是对象，第二个元素是方法.

The callback syntax is a little odd in PHP. What you need to do is make an array. The 1st element is the object, and the 2nd is the method.

call_user_func(array($player, 'SayHi'));

您也可以在没有call_user_func的情况下这样做:

You can also do it without call_user_func:

$player->{'SayHi'}();

或者:

$method = 'SayHi';
$player->$method();