HTML Encyclopaedia

The form tag

The HTML element

<form ...> .... </form>

Once the various boxes within the form have been filled and the "submit" button has been hit the user entered values are transmitted to the server where a CGI back end can process the information and generate whatever reply is required.

A <form> tag has three significant attributes, method, action and enctype.

1. method

   For simple use the method attribute can be set to either get or post. This attribute controls the method by which the user entered data is communicated to the back end program.

   • If the get method is selected then all the data is presented to the backend program in the environment variable QUERY_STRING.
   • If the put method is selected then all the data is presented to the backend program on its standard input.

   Many authors suggest that the put method is preferable but the only reasons for selecting it in preference to get are

   • If your host system (the one the backend runs on) restricts the size of an environment variable. This may well be a problem under MSDOS but is unlikely to cause any trouble if you are using Unix.
   • If you are concerned that the WWW server maintains a publically accessible log of requests. get requests can be inferred from such a log, put requests cannot.

2. action

   The value of the action attribute specifies what is to be done when the form-filling is complete. Its value will be simply a URL, if this is the name of an executable file then the file will be executed, however it may simply refer to a WWW page, however this is unusual.

   Here is an example

   <form METHOD="GET" ACTION="http://www.scit.wlv.ac.uk/cgi-bin/test">

3. enctype

   This determines the method used to encode the form's contents. It defaults to application/x-www-form-urlencoded. It need not be quoted unless you are using the <input> tag with the type attribute set to file when the value should be set to multipart/form-data