<?php

class foo {
    public function test(&$x) {
        static $lambda;
        $lambda = function &() use (&$x) {
            return $x = $x * $x;
        };
        return $lambda();
    }
}

$test = new foo;

$y = 2;
var_dump($test->test($y));
var_dump($x = $test->test($y));
var_dump($y, $x);

?>