Once you have learned to develop using PHP, MySQL, and JavaScript you will be ready to take your skills to the next level using the following reference books:
Dynamic HTML: The Definitive Reference by Danny Goodman (O’Reilly)
PHP in a Nutshell by Paul Hudson (O’Reilly)
MySQL in a Nutshell by Russell Dyer (O’Reilly)
JavaScript: The Definitive Guide by David Flanagan (O’Reilly)
CSS: The Definitive Guide by Eric A. Myer (O’Reilly)