<?php

function f($x) {}
function g($x ) {}
function h ($x) {}

function &i($x) {}
function &j($x ) {}

final class X {

  public function a($x) {}
  public function b($x ) {}

  public static function &c($x) {}
  public static function &d($x ) {}

  abstract private function e($x);
  abstract private function f($x );

}

f(function ($x) {});
f(function ($x ) {});
f(function ($x ) use ($z) {});
f(function ($x)use($z) {});
~~~~~~~~~~
warning:4:14
warning:5:11
warning:8:15
warning:13:23
warning:16:31
warning:19:33
warning:24:15
warning:25:15
warning:26:16
warning:26:19
~~~~~~~~~~
<?php

function f($x) {}
function g($x) {}
function h($x) {}

function &i($x) {}
function &j($x) {}

final class X {

  public function a($x) {}
  public function b($x) {}

  public static function &c($x) {}
  public static function &d($x) {}

  abstract private function e($x);
  abstract private function f($x);

}

f(function ($x) {});
f(function ($x) {});
f(function ($x) use ($z) {});
f(function ($x) use ($z) {});