Well I set up another sketch (it's not really important what it looks like) to test if hyperterminal would work sending serial data to the Arduino, and was successful. I easily toggled my little LED on and off.
This leads me to believe that my PHP is funky. I saw an earlier comment in this thread that I should try opening the serial connection for binary communication which I will try. I'll also make sure to determine what baud rate PHP is sending data at so I can be sure that it's in synch w/ Arduino. Man, I'm so close now I can taste it!
Thanks again all.