I was just reading my daily portion of phpdeveloper.org and encountered this article with 4 ways to become a better developer.

The four options discussed might be obvious to most, but I know from experience that they're not obvious to everyone, so I think it's a good read. I especially like the fourth item, on how PHP developers should focus not only on PHP, but also look at Javascript, CSS and HTML. I think it's hard to build an application that consists of PHP only, and even if you have dedicated graphical guru's to do the difficult HTML/CSS stuff (like we do), developers still encounter a fair share of CSS/HTML and Javascript. And in general, it's good to widen your scope and also read about technologies that you might not use directly, but might encounter in the future.