I'm interested in learning more about design practices in PHP for Database Abstraction & Factory methods. For background, my site is a special-interest social networking community currently in beta mode.

Currently, I've started moving my old code for object retrieval to factory methods. However, I do feel like I'm limiting myself by keeping a lot of SQL table names and structure separated in each function/method.

Questions:

1.) Is there a reason to use PEAR (or similar) if I dont anticipate
switching databases?

2.) Can PEAR interface with the MySqli prepared statements I
currently use?

3.) Will it help me separate table names from each method? (If no, what
other design patterns might I want
to research?)

4.) Will it slow down my site once I have a significantly large member base?