This weekend I went to a bookstore and purchased "PHP 4 Bible" to learn more on Php and this is the best PHP book out there. It is very useful and easy to read. I recommend this book to anyone who wants to learn the basics of PHP and more complex features like MATH and Syntax as well as a chapter on Database connectivity. Check it out.
The one thing I didnt like is that the book didnt come with a cd as some others do but has a site where you can download the examples so you dont have to type them.
http://www.troutworks.com/phpbook/
Buy it... worth it.