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