Website resource guide, web development, intoduction to forms

Forms bring life and interactivity to your documents, allowing interaction with the user, customized pages based on individual preferences, and form the basis of every interactive site.

Forms combine both conventional HTML content and special elements to create pages users can manipulate.

As you might expect, every form begins with a <FORM> tag. The <FORM> tag serves three purposes: It alerts the browser that a form is to be created, it identifies the server-side program that will process the data collected by the form, and it defines the way that the data will be passed to the server for processing.

A classic <FORM> tag looks something like this:

<FORM ACTION="http://server.com/cgi-bin/script" METHOD="post">

  ...

</FORM>

When the user submits the form for processing, the browser collects the values from the form elements and forwards them using the post method to server.com for processing by /cgi-bin/script. The script should produce some HTML as a result, and the browser will display this HTML as a fresh document after the form is processed.

For a form to work correctly, the ACTION attribute must provide the URL of an executable program on the server. You can't supply a document for the action, and you can only supply a program that the server knows about and can run. Scripts are stored by the server assigned in the path directory: cgi-bin.

The program must be able to read its parameters using one of the two methods available: post or get. Each method has its advantages and disadvantages.

The post method packages the form data and sends it to the server in a second, separate transmission after the server-side program has been contacted. It is best used for large amounts of data or forms with many elements. It is also required for certain kinds of form data, notably file transfers. On the down side, writing server-side program to read post data is slightly more difficult. In addition, post-style applications can only be invoked via a form.

The get method tacks the form parameters onto the URL when it invokes the form program on the server. The server pulls them apart and passes them to the program, usually as part of its command line. Thus, get-style applications are easier to write, but only work well with a small number of form parameters. You can invoke these programs without using a form, however, by creating a URL that references the program and appends the parameters as part of the URL.

The one you choose depends on your programming skills, server, and the form you create.

Forms without servers

When forms first came on the scene, their only purpose was to collect data and pass it to a server for processing. As better client-side processing became available through Java and JavaScript, some forms were used to collect data for these client-side programs. In these cases, you need not specify an ACTION or a METHOD; the processing is handled by scripts and code embedded in your document.

The purposes: you need not provide an action, a METHOD, or a client-side application. Simply using the <FORM> tag without any attributes is enough to cause the browser to create the elements within the form.

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Introduction To Forms

Forms without servers