How do I force my script to exit after 5 seconds?

I have a script that connects to a networked device via PHP's socket functions. This device accepts proprietary commands (e.g.: "KPRINT", as seen below), and returns data. However, this device does not have any sort of "EXIT" command to end the processing of events. So it essentially loops forever. I do know that if this device does not return anything after 5 seconds, it will never return anything. So, my question is: how can I force this script to stop after 5 seconds has elapsed? Here's the script: ============================================================ $fp = fsockopen('192.168.3.25', 10001, $errno, $errstr, 5); if (!$fp) {

    echo 'Error...';

} else {

    $command = "KPRINT\r\n";

    fwrite($fp, $command);

    while (!feof($fp)) {
        $buffer = fgets($fp, 1024);
    }

    fclose($fp);

} ============================================================ Thanks!