call_user_func() expects parameter 1 to be a valid callback

Question

I\'m just playing around with the call_user_func function in PHP and am getting this error when running this simple code:

Answer 1

Alternatively to Omar's answer, you can also make printHi() a class static function, so you then can call it from call_user_func('A::printHi') , like this:

class A
{

    public $var;
    public static function printHi()
    {

        echo "Hello";   

    }

    public function __construct($string)
    {
        $this->var = $string;   


    }

    public function foo()
    {

        call_user_func($this->var); 

    }

}

$a = new A('A::printHi');
$a->foo();

See live example