This is useful when you are working with multi page forms. If you want to update some information on one page, for one record, and then move to another page and update the same record some more you will need the primary key id field,

This is applicable to the case where the id field is an auto increment, which is the case seen in most circumstances. 

The code is really simple, lets take a look at how its done. 

This is an interesting article I came across. It is mirrored and the link is provided at the end of the page.

The functions described in this article will allow you to parse unstructured data from HTML pages using PHP and perl regular expressions,

The unstructured data can then be stored in a structured fashion in a database of your choosing.