In fact, I want to get all possible teams:

While my solution addresses the above statement in isolation, taken in context with the rest of the post it is likely lacking. For instance:

• For any given game, do all teams need to have the same number of players?
• For any given game, can a player participate in more than one team?
• For any given game, do all players need to play or can they "sit out"?

I am not sure how much of your code addresses those points either but I am pretty sure it misses how to convert a team to a "number" and its reciprocal. Any ideas on that front?

Specifically for a given partitioning ever person must belong to exactly one team.

Teams do not have to be of the same size.

eg For three people:
1.    A   B  C
2.    AB  C
3.    A   BC
4.    AC  B
5.    ABC
[download]

tomazos,
Assuming it does the right thing, you are going to want to use the integer partitioning code blokhead refers to above and the binary counting I explained. You will not have a contigous range of team reference numbers but they will be guaranteed to be unique and will never be higher than 2 ** $num_of_people.

If I find the time tonight or tomorrow, I will code this for you. If you end up coding it on your own, please post so others can benefit and I won't bother.

Cheers - L~R