Description:
------------
when it comes to var_dump(Mutex::unlock($mutex)),error is reported!


<?php
// using php_pthreads-2.0.10-5.6-ts-vc11-x64 version
$mutex = Mutex::create();

var_dump(Mutex::lock($mutex));

var_dump(Mutex::unlock($mutex));

Mutex::destroy($mutex);

Test script:
---------------
<?php

$mutex = Mutex::create();

var_dump(Mutex::lock($mutex));

var_dump(Mutex::unlock($mutex));

Mutex::destroy($mutex);