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:
· Textboxes
· Textareas
· Drop-downs
· Multi select
· File
· Radio buttons
· Checkboxes
· Buttons
· Hidden
The hidden fields are used to send some data that the user does
not need to see, along with the form. An example of this could
be a form number, so the form processing script identifies which
form has been submitted.
The File field allows users to upload a file. The form
processing script will get the file together with the rest of
the form data. For this field to work properly, you need to
include this attribute in the tag: enctype="multipart/form-data."
Buttons are used to submit or reset the form.
Refer to an HTML guide for full description on the attributes
and syntax of each tag. You may find a guide at
http://www.w3schools.com/tags/default.asp or at
http://www.w3.org/MarkUp/ among many other sites.
When the form is complex, it is useful to group fields in areas
using the fieldset tag. Just place the fieldset tag, then
optionally a legend Section Name /legend tag, then all the
pertinent form fields, and the /fieldset tag after them.
It is possible to use CSS (Cascading Style Sheets) or inline
styles to change the look of the form controls.
You can bring your forms to a different level by combining them
with the usage of scripting langauge like JavaScript. You can
make the form react immediately to certain events, like the user
clicking on a control, or a field changing its value. You can
highlight the field that has the focus, for example. Or count
how many characters have been entered in a text box or a
textarea. You can make calculations and display the results
automatically. The possibilities are endless.
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