Linking stuff

Hi all. I think I might be having a brain-fart afternoon, but I can't think of how to accomplish this. I want these "centers" to be linked to 1 another. If center A links to B and C, I want B to be linked to A and C, and C to A and B. So... it should look something like this: center link

A       B
A       C
B       A
B       C
C       A
C       B

These results will be stored in a database and each of the records is unique. To slightly simplify things (hopefully!), I can just store each of the centers in an array, like so: array(A,B,C,D). I figure I'll have to loop through the array (several times?) and do comparisons with each other one. Basically, I don't want to over-complicate this for myself. Any guiding light would be appreciated on how to link all of these! Thanks ~Philip