code:diesl has posted their list of the top six books that can help you master the PHP language:

If you are new to PHP or are thinking of moving to PHP form other language then the following list of books will provide you with the required knowledge to become a seasoned PHP programmer. Of course, the list is subjective and you may have a different list of books in mind.

Their list is made up of:

• Zend PHP5 Certification
• PHP in Action
• PHP and MySQL Web Development
• PEAR
• PHP Cookbook
• SQL for MySQL Developers