php call_user_func() 用法

例1：

function barber($type){
    echo "you wanted a $type haircut, no problem ";
}
call_user_func('barber','mushroom');

返回：
you wanted a mushroom haircut, no problem

例2：

class myclass{
    static function say_hello(){
        echo "hello! ";
    }
}

call_user_func(['myclass', 'say_hello']);

call_user_func("myclass::say_hello");

call_user_func([new myclass(), 'say_hello']);