Website Design and Programming - Introduction to Web Forms
There is practically no website without at least a form in one
of its pages. Forms are useful to collect data from the website
visitors and users. Once the user submits the form to the
server, a form processing script must get the form data,
validate that the user input matches the expected format for
each field (e.g: email address field must be a string of text
with the format of a valid email address) and process this
information as desired. The script may save it into a database,
send it by email or just do some processing with it and display
the result. Validating the user input is essential to prevent
malicious users from damaging your site.
A form definition in html starts with the form tag and ends with
the /form tag. This tag can have several attributes like method
(GET or POST), and action (the url of the form processing
script). If use the GET method, the form data is encoded in the
action URL. This method is recommended when the form is a query
form. With the POST method, the form data is to appear within a
message body. This is the recommended method when the form will
be used to update a database, or send email, or make any action
other than just retrieve data.
The form fields are used to collect the data. Generally a label
is placed by each field, so the user knows what data to input.
There are different kind of fields, among them: