[SOLVED] Testing semaphore via Ajax

[stockton]

I am attempting to set and clear semaphores from php code called via Ajax and the setting seems to be working but the clear fails with the following message.

Warning: sem_release() [function.sem-release]: SysV semaphore 2 (key 0x6b) is not currently acquired

The php I am using is:-

<?php
//This function takes a GUUID like one generated from the /usr/bin/uuidgen program
//(e.g. ab684e1c-15fa-4241-aa53-65dd3bc55bd6) and strips out all the alpha- characters,
//It will then add together all the numbers and return that for use as a VERY semi-unique key.
//This is done this way for the fact that sem_get()  (which is what this was written for) only takes integers for
//the key value.
function GUUIDtoInt($p_GUUID)
    {
    $retVal = 0;
    $stack = array();
    for ($index = 0; $index < strlen($p_GUUID); $index++)
        {
        $char = $p_GUUID{$index};
        if (is_numeric($char))
            {
            array_push($stack, $char);
            }
        }

    $topChar = array_pop($stack);
    $decimalPower = 1;
    while ($topChar != NULL)
        {
        $temp = (int)$topChar;
        $retVal += $temp;
        $topChar = array_pop($stack);
        }

    return $retVal;
    }

// Program starts here
        $Command = $_REQUEST["Command"];
        $intKey = GUUIDtoInt('b6379c52-d96d-418b-83c3-8aedb5e6cf95');
        echo "Testing semaphore code ".$Command." ".$intKey."<br/>";
        if (!$sem_id = sem_get($intKey))
            {
            $Message="Could not get ID for the semaphore.";
            echo $Message;
            exit;
            }
        if ($Command=="set")
            {
            $Message="Got semaphore ID; acquiring...";
            if (!sem_acquire($sem_id))
                {
                $Message.=" failed.";
                echo $Message;
                exit;
                }
            else
                {
                $Message.=" OK Got it.".$sem_id;
                echo $Message;
                exit;
                }
            }
        else
            {
            if (!sem_release($sem_id))
                {
                $Message.=" Release for ".$sem_id." failed. ".$intKey;
                echo $Message;
                exit;
                }

            $Message="Semaphore released. Other scripts should be able to get it now.";
            echo $Message;
            exit;
            }
?>

What am I not understanding and therefore have done wrong?

[stockton]

If I had applied my mind to the problem before asking the question I would have realised that a semaphore cannot survive the program that created it.

Therefore calling the program via Ajax was a bit thick.

Semaphores are used to stop more than one user from running the same program at the same time.