Rankings check

[Anon]

I have a page that allows a user to rank items #1 through #25 using pull-down menus. There are a possible 100 different items to rank in the 25 spots. When the user submits their rankings, I need to check to make sure that they have selected an item in each slot (1-25) and not selected the same item for any of the rankings, before adding their rankings to a database. Can anyone suggest a logical way to do this using php? Any and all suggestions and ideas are greatly appreciated. Thanks in advance.

[Anon]

checking for all items is fairly easy, I guess. just check that none of the vars isemtpy().

checking if all are different is not that difficult eighter? just browse through all of them, check if the others are different? for the first one, this means checking against 24 others, but for the last but one, you only need to check against teh last one. takes some coding, but fairly easy coding...