simple site counter

I need a simple site counter php script. This simple site counter will take the siteid from a incoming parament in a url (for example: the siteid in [login to view URL] is 'ID5565) and save that data to a textfile ([login to view URL]). Each time that same siteid is called again, I need to increase the value in that text file ([login to view URL]) by 1. If a new siteid is called, then i want it to add a new line in counter.txt. And the next time that siteid is called again, add 1 to the value. Basicly im creating this to count how many hits each pages get (the siteid is created by me so you don't have to worry about it). here's an example of what [login to view URL] will look like. siteid5564:6 siteid3345:2 siteid2222:3 The aboove example says that siteid5564 recived 6 hits, Siteid3345 recived 2 hits and siteid2222 recived 3 hits. if the sideid is not in the [login to view URL] then add new and set it to 1. If the siteid is allready there, then add 1 to the previous value. After that i want to grab the number(hits) and return it to the calling html.