4Chan Replica

I'm making a 4chan replica script based of a moderately modified version of tinybb and I'm having a little trouble finding out how page requests work around here.

Say you wanna get to page 2 og /b/, the @ the end of the url you'd just type in "/g/2" right?

Problem is, I'm not sure how 4chans script uses that arg, say you appended "/" to the url as so "/g/2/" it doesn't work, so that tells me this is not a directory right?

How the fuck do I pick this up in my php script so I can know what page to deliver?

You can see it here http://autoitunderground(.)tk/chan/b/

>>20 I wish wasn't an asperger, sometimes I find myself rubbing my dick on my chiguaguas quarter inch vagina , don't blame me, the world just doesn't understand me so I seclude my self in my room void of social activities because I find people's conversations dull and boring because I'm on another intellectual spectrum, any way, I'm to ugly to get laid by any chick who is normal so that's why I refer to a legitimate server side scripting language years in development as a "toy language", due to my meticulous obsession of sitting behind my monitor for days on end all while my ass is developing ulcers from so much sitting every day, but I don't care, since no one will ever appreciate my anal cavity like my dog spot, sometimes I even think my mother wishes she aborted me because I'm just a parasite leeching off of her life, I've failed socially so I decided to pursue the goal of understanding low level programming languages which every one knows that people who are good with it, generally display autistic characteristics and anti-social behavior, I mean, because really, who else will spend their life behind a monitor staring at a luminous screen which will most likely depreciate my vision soon.