Should we presume you have little or no knowledge of PHP?
If you have not already done so, I suggest you take a look at Google Docs whereby you can create a spreadsheet (instead of a database) and create an input form in a clicky-pointy kind of way that you then embed in a webpage.
google docs forms
The first paragraph of the first link on that list (for me anyway) states:
"Forms are a useful tool to help you plan events, give your pupils a test or collect other information in an easy, streamlined way. A Google form is automatically connected to a spreadsheet with the same title. When you send a form to recipients, their responses will automatically be collected in that spreadsheet."