To do

<?php
$fp = fopen(“/tmp/lock.txt”, “w+”);
if (flock($fp, LOCK_EX)) { // do an exclusive lock
fwrite($fp, “Write something heren”);
flock($fp, LOCK_UN); // release the lock
} else {
echo “Couldn’t lock the file !”;
}
fclose($fp);
?>
http://us3.php.net/flock


read – write Berkeley DB
Response handling in response.c