Enhance existing PHP application in Codeigniter

Has a very small PHP projecting that needs to be enhanced to it. It is built in Codeigniter. It connects to a mySQL database and SQL server database. Need two(2) changes - Part of the app generates a random 4 digit order code (XXXX) and I need that be changed to a new format (RP0000XXXX). Also end of the generating that order code, I need it to post some existing data from the mySQL database to a new API (straight post function). I can provide you with entire Codeigniter Code, a copy of MySQL database and two sample tables(CSV) from the MS SQL Server that you will need to import into your test MS SQL server environement.