php - Recursively linking records -

i have table timeslots users can sign for. on administrative end, admin-user can choose 'link' 2 timeslots together, says end-user, 'if sign 1 of these timeslots, must sign other timeslots linked it.' these links stored in table has 2 columns, 1 being id of timeslot requiring link, , other being id of timeslot being linked to.

how can make such when linking 1 timeslot another, both depend on other being selected. needs recursive other linked timeslots well, following example:

admin says:  #1 linked #2 #3 linked #2  therefore:  #1 linked #2 #2 linked #1 #3 linked #2 #2 linked #3 #3 linked #1 #1 linked #3 

what best way accomplish this? right i'm trying put information link table, if there's way can more php , less sql work also. provide code sample, don't think helpful.

edit: conceptual answers fine. don't need code written me unless demonstrative purposes.

one approach may table of 2 columns in form of: node_id, , link_id.

in case, node_id timeslot id. example above, rows be:

1    1 2    1 3    1 

where 1, 2, 3 in first column timeslots, , 1 in second link.

hypothetically let's add timeslots 4, 5, 6, 7, , 8 links 2, 3, , 4.

4    2 5    3 6    2 7    4 8    2 

this translates to:

pick 4, must pick 6 , 8 (all link 2). pick 5, you're done (only member of link 3). pick 6, must pick 4 , 8 (all link 2). pick 7, you're done (only member of link 4). pick 8, must pick 4 , 6 (all link 2).