Here is a list of e-books that i have found on php I hope you find them useful.
A good starting book is php5 for dummies - you can find this in pdf here...
If you would like to learn about php and hacking/exploiting you can find a pdf called the "black art of php" here...
For users who want to become better programmers with php5 then this book is a must PHP5 power programming.
Most of these books were published in 2005 or 2006 and *may* still be under copyright. If this is the case in your country then use these links for evalution purposes only. If you like the book buy it.
Let me know if these books interest you - i have found plenty more and am happy to share but only if people want me too.
Hope you Enjoy