Here https://github.com/miraheze/mediawiki/blob/REL1_37/includes/libs/objectcache/utils/MemcachedClient.php#L788 does not support ipv6.
ip-utils provides a method which could be used:
splitHostAndPort( $ip_and_port )
so this could become
$server = splitHostAndPort( $ip_and_port ) if ($server === false || !isset( $server[1] )) return false; $ip = $server[0]; $port = $server[1];
I think ?