Description:
------------
---
From manual page: http://www.php.net/function.flock#refsect1-function.flock-
examples
---
Example should be modified to add fflush() as below.  There is no point in 
gaining an exclusive lock if you release it before flushing output.

<?php

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

if (flock($fp, LOCK_EX)) { // do an exclusive lock
    ftruncate($fp, 0); // truncate file
    fwrite($fp, "Write something here\n");
    fflush($fp); // flush output before releasing lock
    flock($fp, LOCK_UN); // release the lock
} else {
    echo "Couldn't get the lock!";
}

fclose($fp);

?>

Actual result:
--------------
Saw a corrupted file that seems to indicate that output is not automatically 
flushed when an exclusive lock is released.