Splitting a CSV file

Hi there everyone, I'm writing an automation system to automatically insert data into a mysql database from a CSV file, and it works great - until I try to insert a large file, then it just doesn't do anything. I've set my PHP filesize to 10 Megs so that's not the issue, and a server timeout isn't the issue either. So, is that a way that I can split a CSV file into 2 files if it's larger than a certain size so that I can still use the automation I am working on? Actually, I won't see the files as it's for a company who just wants to be able to select their CSV file (No matter what size) and it will insert it automatically, and as I said it does work on small files but not large :-( Any help would really be appreciated. Chris