Let pick some of the low hanging fruit for optimizing you PHP application or PHP framework or whatever PHP.
1. Install the on your server.
2. Don't start sessions - unless you really need to.
3. Don't connect to the database - unless you really need to.
4. Don't include large libraries you don't need to use.
Using these 4 rules you really get a lot of mileage, at little cost - hence the low hanging fruit...
Consider that you are optimizing your front page for huge spikes...
Do you need to start sessions for all users?
Do you need to connect to the database?
Do you need to include lots of classes (that you are not going to use
And the APC cache really makes a difference...
A place where I implemented this is: