Zend Developer Zone is always a very good resource for PHP developer, the ZendCon Sessions are one of my favorite and important references:

Zend Developer Zone

“The ZendCon Sessions” releases a new session each week while it’s in production. These are the live recordings of sessions taught at ZendCon. If you missed the last ZendCon, this is the next best thing to actually being there.

zendcon-sessions-logoIt currently has 20 episodes about all important PHP related issues like Security, Performance and Framework etc.

Currently most of the episodes are 2007 Zend Conferences but still very useful now and future, it also provides podcasts to download:

The ZendCon Sessions Podcast is live recordings of sessions that have been given at previous Zend Conferences. Combined with the slides, they can be the next best thing to having attended the conference itself.