Does setting a memcached key that already exists refresh the expiration time?

Question

Let's say I have the following code:

Memcached->set('key', 'value', 60); (expire in one minute)

while (1) {
    sleep 1 second;
    data = Memcached->get('key');
    // update data
    Memcached->set('key', data, 60);
}

After 60 iterations of the loop, will the key expire and when reading it I'll get a NULL? Or will the continuous setting keep pushing the expiration time each time to 1 minute after the last Set?

The documentation mentions this, and I've tested this in different contexts and I'm pretty sure I got different results.

Answer 1

Ok, found my answer by experimentation in the end...

It turns out "Set" does extend the expiration, it's basically the same as deleting the item and Setting it again with a new expiration.

However, Increment doesn't extend the expiration. If you increment a key, it keeps the original expiration time it had when you Set it in the first place.

Answer 2

If you simply want to extend the expiration time for a particular key instead of essentially resetting the data each time, you can just use Memcached::touch

With the caveat that you must have binary protocol enabled according to the comment on the above page.

$memcached = new Memcached();
$memcached->setOption(Memcached::OPT_BINARY_PROTOCOL, true);
$memcached->touch('key', 120);