php and DB2

hi to all, my IT director got an idea to replace mysql with DB2. more "power/flexibility/stability/security..." though, for our needs, I think mysql is just fine and enough. the business we are doing is promotional products and all online orders we have are ONLY from our sales people. with 200-300 orders per day and averge of 5 items per order I think we really don't need that replacement. though, don't know how php works with DB2 (assuming same quality as with mysql). can anybody give me some ideas and "reasons" to present to boss to NOT replace mysql with DB2? thanks. -afan