<?php
class C {
    private function f() {}
    static function __callStatic($name, $args) {}
}

class B {
    public function __construct() {
        $isCallable = is_callable(array(new C, 'f'));
        var_dump($isCallable);
    }
}

new B();

Class E {
   private function f() {}
   function __call($name, $args) {}
}
$isCallable = is_callable(array('E', 'f'));
var_dump($isCallable);
?>