PHP / MYSQL上传，导入.csv文件到mysql-process-table设计

I want to let users upload their contacts from a .csv file (exported from various contact management programs) to the server and then save it in mysql. From what I've read on SO and elsewhere, MYSQL can import the data using LOAD DATA INFILE. It also seems like there is a LOCAL option to get it from the client side. My three-part question is: Do I need to use file upload to get the file to the server or can I directly access it via the LOCAL option of LOAD DATA INFILE? Since the application will service multiple users with their contacts, should I put all the contacts in one table? Since different users will have different structures in their .csv files what is the best approach to handling discrepancies in fieldnames/schema in the different .csv files? I want to let users upload their contacts from