mimic facebook app invite box

[monkeytooth]

Alright, im not exactly sure if there is a specific technique to this or not..

 

If you use facebook and you play any of the apps like mafia wars for example. There is always an invite friend function. I want to create a function similar to that on one of my sites. Now listing out the people to add, selecting them from the list and all else, ok got that part. What I am mostly curious about is how would I go about making the script remember that on a user to user basis.

 

Not everyone is going to invite everyone else with what I have in mind but they do have a list of thousands of people to invite with what it is I want to do thats similar. Is there a specific technique I should be looking into for this? Cause I can't picture an array being a feasible option considering how large it would get for any one individual over time. I can't picture a table specific to that either as that would eventually get to huge as well a row per person associating one person to another so to speak. All in the name of remembering that this person already invited this person so it wouldn't display the other person in this persons list next time they come and it loads.

 

I mean it is obviously a possible thing to do, but I just can't wrap my head around how to store something like that and work with it via php. Any ideas?