PHP Memcached Session Locking Enable

Maybe try something like $(field_name)_is_locked = true when you start then when you are done $(field_name)_is_locked = false and pass the variable to the server when you update it.

There's nothing built in no, but you can write stuff yourself to make your code atomic.

$key = 'lockable_key_name';
$lockkey = $key.'##LOCK';

if($memcached->add($lockkey, '', 60)) {
    $storedvalue = $memcached->get($key);

    // do something with $storedvalue
    $memcached->set($key, $newvalue);

    // release
    $memcached->delete($lockkey);
}

In your code you could check for the lock by doing:

if(!$memcached->get($lockkey)) {
    // then do something
}

If the get method returns false then there's no lock, or the operation has hung and passed the 60 second timeout specified in the add call above.

Since you were asking for credible/official sources:

The memcached extension supports session locking since version 3.0.4, according to the changelog document on the PECL extension page: http://pecl.php.net/package-info.php?package=memcache&version=3.0.4

If you happen to run an earlier version (it means that your version of the memcached extension is more than 4 years old), you are out of luck and should upgrade.