It's listed here on the PS4 Beta overview page: http://eu.finalfantasyxiv.com/lodest...f5d9f6dbfc90e6

Quote Originally Posted by Final Fantasy XIV Lodestone
Participating in Beta Test Phase 2
Starting Friday, April 4, 2014, FINAL FANTASY XIV: A Realm Reborn will be available for download from the PlayStation®Store. No registration is necessary after downloading the game client.

* Please note that a different game client is required to participate in phase 2 of the beta test. Users who participated in phase 1 are required to download the new game client.
So Suki is right - if you were in the PS4 Phase 1 beta you need to download the new client to participate in phase 2 (this was the same as it was during the original ARR Beta last year for the PC and PS3 incidentally.).