I could cop out here and say that the advantages of PHP are too many to list in such a small book as this, but it seems that some people need convincing of PHP's inherent greatness, and I am very happy to oblige.
If you are not new to PHP, I still recommend you at least glance over the contents of this chapter. I find that programming in PHP is very often like playing my guitar. I can be sitting in my study strumming idly on my 12-string like I've done thousands of times before, only this time I play a different chord sequence, or strum the strings in a different manner than normal, and I think "Hey, that's cool... how come I never found that before?"
At various points in my PHP programming past, I have stumbled across functions or functionality in pretty much the same way, and responded with pretty much the same response! If you're the same, then definitely read on - it doesn't hurt to see what's on offer.