I had to migrate PHP sessions from file based sessions to Memcached based sessions. I couldn't shutdown the servers involved for the split second it would take because all of my users would lose their current sessions. I put this together to migrate the file based sessions to memcached sessions.

migratesessions.php

<?php

$m = new Memcached();
$m->addServer('localhost', 11211);

$sessions = scandir("/var/lib/php/session/");
if($sessions)
{
        foreach($sessions as $s)
        {
                if(!in_array($s,array('.','..')))
                {
                        $session_name = str_replace("sess_","",$s);
                        $session_contents = file_get_contents("/var/lib/php/session/".$s);
                        $m->set("memc.sess.key.".$session_name,$session_contents);
                        print ".";
                }
        }
}

?>

Few things to change for your environment.

• memcached server
• memcached port
• PHP session file location
• PHP session file prefix
• PHP session memcache key prefix