closure_extension.php

<?php
// public ReflectionMethod::getClosure ( object $object ) alternative
function toClosure($class_name, $method_name, $obj = null) {
    if (!is_null($obj) and !is_a($obj, $class_name)) throw new \InvalidArgumentException('invalid object is given.');
    $func = new ReflectionMethod($class_name, $method_name);
    if ($func->isStatic()) {
        return function() use($func) {
                   $func->invokeArgs(null, func_get_args());
               };
    } else {
        return function() use($func, $obj) {
                   $func->invokeArgs($obj, func_get_args());
               };
    }
}