Calculations using PHP and a flat file

[dp2]

Could some one point me in the right direction.

 

Firstly, I would like to find out how to add a set number say 10, via a form to a flat file field that not only deletes and replace but to add the existing number together to produce a total. A sort of counter in units of 10.

 

I'm working on a simple afflicate script that adds rewards points to a registerd user who has refered  a new user to a basic subscription service. The new user types in the users unique promotion code and is directed to a page that offers a discounted rate (A page with a Paypal button link)

 

The promotion code I thought could be the userid number to access the correct line and then adds the points.

 

I can add the points to the field but it replaces the other record.

 

In general what are all the calculation possibilities

 

Thanks

[.josh]

google php flatfile hit counter.  A billion scripts, example, tutorials, etc.. blahblahblah.  Change it to add 10 instead of 1.  Bask in the glory of self sufficiency.