I recommend the book "PHP and MySQL Web Development" it was that best book ever bought, explains things in simple ways nice and easy to read I got it from amazon for about $40, I also got "Professional PHP4" this book is also helpful although the explainations are very complex most of the time.
Also its helpful to downlaod the php manual theres a windows help file there somewhere just saves you time searching the internet you can get that from php.net.
one of the advantages of php.net is that they give nice clear examples where with the books the functions are used with conjunction of others often meaning you have to search through a page of script to find what you want