The Pragmatic Programmer is worth a read: not coding language specific, but more about general concepts and practices.
Essential PHP Security is a short book that gives you a good overview of the things you need to think about in that regard.
Assuming you mean AAA web content accessibility, that's more an HTML/CSS/JavaScript issue than a PHP one, and how important it will be to you depends on how much client-side work you do and how important it is that the site in question be accessible. (While I'd like to think that all sites would want to maximize accessibility, realistically, for some it's less important, while in others there may actually be legal requirements to be accessible.)
I drink very little caffeine any more: it does not-so-nice things to me, but I do still miss it.