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php – Fatal error: Call to undefined function sem_get()

Posted by: admin July 12, 2020 Leave a comment


I’m new to PHP and I’m trying to run code I got from someone else on my Windows development machine. I installed PHP 5 and Apache 2.2, but when I try to run it I get the error:

Fatal error: Call to undefined function sem_get()

The line it’s being thrown from is:

private function UpdateCounter($semkey, $memkey, $count)
    $sem_h = sem_get($semkey, 1);//this line is the problem
How to&Answers:

The sem_get() function is provided by the Semaphore, Shared Memory and IPC component.

Quoting the introduction of it’s manual section :

This extension is not available on
Windows platforms.


I don’t know if that will work as expected, but I found a workaround for sem_get on Windows:

if (!function_exists('sem_get')) {
    function sem_get($key) {
        return fopen(__FILE__ . '.sem.' . $key, 'w+');
    function sem_acquire($sem_id) {
        return flock($sem_id, LOCK_EX);
    function sem_release($sem_id) {
        return flock($sem_id, LOCK_UN);

Also, I needed ftok on Windows too:

if( !function_exists('ftok') )
    function ftok($filename = "", $proj = "")
        if( empty($filename) || !file_exists($filename) )
            return -1;
            $filename = $filename . (string) $proj;
            for($key = array(); sizeof($key) < strlen($filename); $key[] = ord(substr($filename, sizeof($key), 1)));
            return dechex(array_sum($key));