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A form on a web page allows a user to enter data that is, typically, sent to a server for processing and to mimic the usage of paper forms. Forms can be used to submit data to save on a server (e.g., ordering a product) or can be used to retrieve data (e.g., searching on a search engine).
XHTML/HTML forms
A form in XHTML or HTML is by far the most common way to use a form online.
The following are a list of elements that can make up the user-inputting portion a form:
- input field
- text – a simple text box that allows input of a single line of text
- checkbox – a check box
- radio – a radio button
- submit – a button that tells the browser to take action on the form (typically to send it to a server)
- textarea – much like the text input field except a textarea allows for multiple rows of data to be shown and entered
- select – a combo box that displays a list of items a user can select from
These basic elements provide most possible graphical user interface (GUI) elements, but not all. For example, there are no equivalents to a combutcons, balloon help, tree views, nor grid views. A grid view, however, can be mimicked by using a standard HTML table with each cell containing a text input element. A tree view could also be mimicked through nested tables.
The sample image on the right shows all of these elements:
- a text box asking for your name
- a pair of radio buttons asking you to pick your sex
- a select box giving you a list of eye colors to choose from
- a pair of check boxes to click on if they apply to you
- a text area to describe your athletic ability
- a submit button to send it to the server
Combined with programs
Forms can be combined with various scripting languages to allow developers to create dynamic web sites. This includes both client-side and/or server-side languages.
Client-side
The de facto standard client-side scripting language for web sites is JavaScript. Utilizing JavaScript on the Document Object Model (DOM) leads to the method of Dynamic HTML that allows dynamic creation and modification of a web page within the browser.While client-side languages used in conjuction with forms are limited, they often can serve to do pre-validation of the form data and/or to prepare the form data to send to a server-side program.
Server-side
Server-side programs can do a vast assortment of tasks to create dynamic web sites — from authenticating a login through, for example, Lightweight Directory Access Protocol to retrieving and storing data in a database to spell checking to sending e-mail — quite unlike client-side programs. Most (all?) server-side program requests must pass through the web server's Common Gateway Interface to execute the program to actually perform the tasks.The advantage of server-side over client-side is the concentration of functionality onto one computer (the server) instead of relying on each web browser implementing all of the various functions the same. This very problem is quite evident to any developer who writes JavaScript code for multiple browsers.
Scripting languages are the most common server-side programs used for web sites, but it is also possible to run compiled programs.
Some of the scripting languages commonly used:
Some of the compiling languages commonly used:
PHP
PHP is one very common language used for server-side languages used and is one of the few languages created specifically for server-side programs.A PHP script may:
- display the information on another page (ex: asking for a user's name and then displaying it on the web page)
- act as a log on interface
- post the data to a database (ex: mySQL, an ASCII file, etc.)
- store the information on the viewer's computer in an HTTP cookie
- generate an e-mail, either using the data or including said data in the e-mail's contents (possibly as an e-mail attachment)
The HTML form learns to where it shall pass the data from the action attribute of the form's HTML element. The target PHP file then retrieves the data either through POST or GET (see HTTP for more information), depending on the programmer's preference. Here is a basic form handler PHP script that will post the form's contents, in this case "user", to the page using POST:
form.html
form_handler.php
$name = $_POST*; echo "Hello, ". $name ."!
"; ?>
XForms
See also
External links
"Form (web)"