PHP/Script Basics

Beginning PHP 5 and MySQL: From Novice to... is one I own, and although it covers many advanced subjects, the book begins with an introduction to key, and basic programming principals, which would probably be helpful to non-programmers.

Before you buy a book, you may considering taking the tutorial here:
PHP Tutorial
If you're like me, having a book can be helpful, however, since they are so much easier to read. You should also be aware that PHP's official site has extremely thorough documentation:
PHP: Hypertext Preprocessor

I agree SitePoint is an excellent resource. I have a whole wall of there Blue and Orange books.

Ahhhh, actually, it's pretty easy.

Hmmm, I've been a programmer since I was in elementary school. Aside from the programming language itself - I mean generically and not language-specific, you need to know 4 things to start using PHP and referring to some language reference book frequently. PHP has way lots of inherent functions and libraries to fulfill any tasks you can imagine, thousands of them. But DON'T PANIC because even the greatest of PHP developers can't remember them all and it's not for us to remember after all.

The 4 things are:

1. Codes are executed line by line - fair enough, as we do things one by one, one after another, in natural sequence.
2. Codes make choices upon given conditions, executing some branching codes upon condition 1 while executing the others upon condition 2. So basically, execution branching on conditions.
3. Codes repeat things that are repetitive, executing a certain group of codes again and again until some condition is met.
4. Codes can be grouped - modularized. In parlance, code modules can be functions, classes and even structured library. A group of code, or a module needs some input to produce output.

That's all. Programming is not that hard. PHP is the right choice for a beginner, it's super easy and straightforward to catch on.

OR:

1. Code only does one thing at a time, one after the other
2. It can make choices based on yes or no answers (BOOLEAN LOGIC IS WHAT TRIPS MOST PEOPLE UP)
3. It can loop and do the same thing repeatedly until a choice is correct (count, or compare)
4. You can take a bunch of code and wrap it in something else so you can use it in many places without caring about how it does the job.

Classes can be particularly hard to explain, but the other stuff is generally OK. Gets harder again when you introduce event handlers and threading though.