Unique code ID function

Unique code/ID function : scan through existing db, should be unique, auto-generate with prefix if user chooses (like STOP1 STOP2... R01, R02...)

function unique( code_to_check, stop/route) first param is text string of user-entered code. second param tells whether this is for stop or for route (and based on that function scans the stops or routes database) returns : yes/no to say unique or not, and suggested unique code if not.

Note: In addition to user-assigned unique code, system could also assign a permanent unique id which will never change for that stop while user-decided unique code might change. This system unique code should be created by system itself when new stop/route is created, not by this unique code function. Eg: the way wordpress assigns a unique id number to anything created, whatever the post type etc be.