It looks like your apt sources got out of sync somehow. Oneiric has 5.3.6-13ubuntu3.1 in the release pocket, and 5.3.6-13ubuntu3.2 in updates and security.
I am also able to install php5-mysql without problems on an up to date 11.10 system, so I believe this is most likely local problems to your system. Possibly try 'apt-get update' and also check 'apt-cache policy php5-mysql' to find out what source that old version is coming from. ** Changed in: php5 (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu Server Team, which is subscribed to php5 in Ubuntu. https://bugs.launchpad.net/bugs/886423 Title: Can't install php5-mysql in Ubuntu 11.10 due to unmet dependencies To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/php5/+bug/886423/+subscriptions -- Ubuntu-server-bugs mailing list Ubuntu-server-bugs@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-server-bugs