$sem_id = sem_get($user_id , 1);
if ($sem_id === false)
{
    return  "Fail to get semaphore";
}
 if (! sem_acquire($sem_id))
{
    sem_remove($sem_id);
    return  "Fail to aquire semaphore $sem_id.n";
}
if (error) {
    sem_release($sem_id);
    sem_remove($sem_id);
    return 'fail';
}
 if (!sem_release($sem_id))// this line throws error
    return  "Fail to release $sem_id semaphore.n";
if (!sem_remove($sem_id))
    return "Fail to remove $sem_id semaphore from SysV.n";
return 'ok';