How do I add "friends" function in PHP?

Hello stack overflow I need help with this problem. Ok, I have a flat file datab开发者_运维问答ase in php it records users , hobbies, fav movies and all. Now i want to add a buddy system so they can have friends and send messages to each other in php without SQL.

Consider having another table (er, flat file?) that maintains links. "Mark" and "John" are buddies if there exists a row in this table (ff?) that links "Mark" and "John". I'd recommend using some sort of index (you know, like a primary key).

Suppose you have a users table (or flat file, whatever, it doesn't matter that much) that contains users and some data, it looks like this:

UID | Username | Hobbies
------------------------
1   | Mark     | Swimming, Sailing, Skiing
2   | John     | Biking, Paragliding
3   | Suzie    | Flying, Skiing

And you have this other friends table (again, flat file, whatever...):

Pair ID | A  | B
----------------
1       | 1  | 2
2       | 2  | 3

We've encoded in this friends table that Mark and John are friends, and that John and Suzie are friends, but with the absence of relation 1 and 3, we know that Mark and Suzie are not friends (at least according to our records).

Note that if you want to get all of John's friends, you have to find all rows in your table (or file) that have John's UID (here = 2) in either column A or column B.

Well I am afraid there's no magical answer or a magical PHP function you can call to enable this behavior.

If we are to help you at all we really need some more to work with.

If you really, for mysterious reasons, decide to stick without a SQL database - then I would probably still "tilt" towards a SQL like way of storing it. Assuming you're currently storing each user as a row in a file, with each "field" separated by some character - simply add another "field" in the file and have this containing each "id" of every user that they're friends with (id, being whatever you use for that, could be a name as long as it is unique).

As for the messages, another flat file describing the message itself, sender and recipient would probably be the way to go.

Now the real question is, why so eager to avoid using a SQL database? If it is because of having to install a database, try SQLite