I Have a web application that will support a large number of connections. Each time a session is created, or a refresh is called, I will run a service that will collect data and store it for viewing. Then using php, read this data from somewhere, and display it back to the user. My question is; If i'm only reading and writing from a single table with 5 columns and 50~100 rows(per user), would it be faster to store this information in flat file(s) and read from it?
You'll only know for sure by benchmarking it, but keep in mind that the developers of the RDBMS systems have already taken care of the necessary optimizations to move data in and out of database tables, and MySQL has a strong API for PHP, supporting transactional writes.
I would go for the database over flat files for sure, but benchmark your own situation.