For all those who are fans of PHP web language, why do you love it so much? What do u do with it? What can you do with it?

Im asking because I have been web-designing with mostly html, minor javascript, minor css, and minor php since 2000. and my friend tossed me his brand new PHP book, and i dont know if its worth my time. i havent a clue of possible benefits except for a "contact us" email form and mySQL database.