491860 PHP coded csv file comparision project

I have a website that i upload csv files to. The project is to compare the current csv file with an updated csv file. just to insure that the data is not doubled and that all new changes are made. example current csv file "wheel,12345,45,120,25,100" Updated csv file "wheel,12345,23,120,25,100" the first 2x feilds are NEVER changed but the last 4 fields can be changed I would like this to be in a php format so that the work is done online