I've been working a little bit on a Facebook application, but when I registered a new user to test the friend interaction the new user got a uid (100000XXXXXXXXX) that seems to big for php to handle.
Saving the number in the database results in the same value (2147483647). I'm guessing this is also PHPs fault, as I would believe the uid would fit in an unsigned bigint?
I'm not quite sure where to go from here, any suggestions?
The fix is to store the UID as a string always. Use the VARCHAR field type in MySQL and you will be fine.
In general, many database gurus will tell you that interpreting another application's foreign keys (like UID in this case) is bad bad bad and you should handle them as opaque text.
I'm using BIGINT UNSIGNED for a couple applications and it works just fine.
What type of MySQL field are you storing the UID data in? An unsigned bigint can store up to 18446744073709551615. (See http://dev.mysql.com/doc/refman/5.0/en/numeric-type-overview.html)
Simply update your schema via something like...
ALTER TABLE <table name> MODIFY COLUMN <column name> BIGINT UNSIGNED NOT NULL;
...and I suspect all will be well.
NB: You'll want to try this on a backup to ensure I'm not deeply incorrect. :-)
Facebook recommonds to store it as a BIGINT unsigned (http://wiki.developers.facebook.com/index.php/User%5FID).
For PHP, you'd store it as a string (because, ultimately, if you're going to use it, it's going to be displayed on the page or in JSON data or something else that's stringy. There's no real need to perform arithmetic on that number).