$fp = fopen("/tmp/lock.txt", "r+");

if (flock($fp, LOCK_EX)) { // do an exclusive lock
    ftruncate($fp, 0); // truncate file
    fwrite($fp, "Write something here\n");
    fclose($fp); /// tohel tu mema byt
    flock($fp, LOCK_UN); // release the lock
}

/// ma to by zde
//fclose($fp);

<?php
header("Content-type: image/jpeg");
$soub="mys.gif";
$handle = fopen ($soub, "r");
$contents = fread ($handle, filesize ($soub));
fclose ($handle);
echo $contents
?> 

header("Content-Type: image/gif");

readfile($filename);