There is a bug (may be it is a feature)

When I store multiple keys at once instead of storing values (for example int(0) ) it stores something like

i:0;

The reason is in https://github.com/zendframework/zend-cache/blob/master/src/Storage/Adapter/Memcached.php#L403

Code below fixes issue

$namespacedKeyValuePairs[$this->namespacePrefix . $normalizedKey] = $value;

It seems to me that it may be related to all other adapters cause all of them have the same code.

I could provide test if it is necessary.