<?php
$genericLockFile = './' . $_SERVER['PHP_SELF'] . explode('.', $argv) . '.lock';

if ($genericLock = fopen($genericLockFile, "w")) {
    // create the lock
    if (flock($genericLock, LOCK_EX | LOCK_NB)) {
        echo "***************\n
        Creating lock for this script...\n
        ***************\n";
    } else {
        die("Lock exists for this file. Stopping script..\n");
    }
} else {
    die("Script requires a lock but could not be created!\n");
}

// release the lock if this script is executed
register_shutdown_function(function() use ($genericLock) {
    echo "***************\n
    Releasing lock for this script...\n
    ***************\n";

    flock($genericLock, LOCK_UN);
    fclose($genericLock);
}, $genericLockFile);