my php-driven thoughts

I've been invited to upcoming PHP conference which will be held at Kaunas Technical University (KTU), but i haven't decided yet what topic should i cover? It's been a while since the last PHP conference. I have organised two of them my-self (with a lot of help from my friends, of course), but now i ran out of ideas.

During previous conferences (there were 4 of them) I've spoken about such things as PHP basics, PHP OOP basics, hierarchical data structures in relational database systems.

I've led two seminars for high-scool teachers about web developement with PHP.

Now i feel rather confused about what topic to choose. In upcoming conference there will be such topics as:

• Objects for work with databases
  
• Cacheing strategies
  
• Planning of PHP projects
  
• Security - situation of Lithuanian internet.
  
• Migration from PHP to ASP.NET
  

I'm still pondering...