I guess you mean 5 submissions of a particular form or forms will lead to a link appearing in a menu or some other navigation that will allow them to do something?
If so, probably the best way is to create a session or cookie, on the submit of the form, check for the cookie (or session, or both) and if there isn't one set one and set its value to 1.
So they have a session var or cookie (or both) with the value 1.
If the session var exists or the cookie exists, you increment the value stored and save.
Using a cookie as an example.
1. User submits form
2. Site checks for cookie called "formcount"
2.1. If formcount does not exist, set cookie formcount with a value of 1
2.2. If formcount exists, read the value, increment by 1 and re set the cookie
3. if formcount = 5, allow the link to appear.
That kind of thing.
Thats actually a cruddy example, you'd want to elaborate on it and probably use sessions over cookies (unless you want the count to persist past the current session), but thats the type of process you'd want to take. If you have a membership system you'd probably tie it into that, with some kind of indicator.
This post has been edited by FizixRichard: 26 January 2012 - 04:13 PM