Ian Kallen weighs in with his thoughts on PHP vs J2EE when it comes to scalability. He points out that most performance issues with Web applications stem from mistakes that can be made with any platform.
Update: More from the PHP side of things. Here’s Jeremy Zowodny arguing against using database abstraction layers in PHP, and instead using the DB-specific functions and wrapping them in a DAO (data access object) layer, although I doubt that’s what PHPers call it. In the Java world, I’ve become a big believer in the use of persistence layers (or at least Hibernate) over JDBC mainly because it’s a huge savings in terms of lines of code that you have to write. Since I’ve been trying Spring, though, I’ve decided that abstracting away Hibernate with Spring and a DAO layer is the way to go. I’ll probably change my mind again soon.