<?php

class A {
    private function method($x) {}
}

class B extends A {
    public function test() {
        $x = 1;
        $this->method($x);
        var_dump($x);
    }
}

class C extends B {
    public function method(&$x) {
        ++$x;
    }
}

(new C)->test();

class D {
    private function method(&$x) {
        ++$x;
    }
}

class E extends D {
    public function __call($name, $args) { }

    public function test() {
        $this->method($x);
    }
}

(new E)->test();

?>