Here's an example where a visitor can fill in a form and when form is submitted, the server stores the data in a database. The next time a visitor comes to the same page, the data that was uploaded by the previous visitor is now on display.
Look through the code and read the comments for detailed explanations. In summary, the form input is parsed and saved onto the end of a "comma separated value" data file. Then the file contents are read back, turned into html table rows, and substituted into a placeholder in the original form.