An HTML form is a section of a document containing normal content, markup, special elements called controls (checkboxes, radio buttons, menus, etc.), and labels on those controls. Users generally “complete” a form by modifying its controls (entering text, selecting menu items, etc.), before submitting the form to an agent for processing (e.g., to a Web server, to a mail server, etc.)

 <FORM action="http://somesite.com/prog/adduser" method="post">
    <P>
    <LABEL for="firstname">First name: </LABEL>
              <INPUT type="text" id="firstname"><BR>
    <LABEL for="lastname">Last name: </LABEL>
              <INPUT type="text" id="lastname"><BR>
    <LABEL for="email">email: </LABEL>
              <INPUT type="text" id="email"><BR>
    <INPUT type="radio" name="sex" value="Male"> Male<BR>
    <INPUT type="radio" name="sex" value="Female"> Female<BR>
    <INPUT type="submit" value="Send"> <INPUT type="reset">
    </P>
 </FORM>

17.2 Controls

Users interact with forms through named controls.

A control’s “control name” is given by its name attribute. The scope of the name attribute for a control within a FORM element is the FORM element.

Each control has both an initial value and a current value, both of which are character strings. Please consult the definition of each control for information about initial values and possible constraints on values imposed by the control. In general, a control’s “initial value” may be specified with the control element’s value attribute. However, the initial value of a TEXTAREA element is given by its contents, and the initial value of an OBJECT element in a form is determined by the object implementation (i.e., it lies outside the scope of this specification).

The control’s “current value” is first set to the initial value. Thereafter, the control’s current value may be modified through user interaction and scripts.

A control’s initial value does not change. Thus, when a form is reset, each control’s current value is reset to its initial value. If a control does not have an initial value, the effect of a form reset on that control is undefined.

When a form is submitted for processing, some controls have their name paired with their current value and these pairs are submitted with the form. Those controls for which name/value pairs are submitted are called successful controls.

17.2.1 Control types

HTML defines the following control types:

buttons

Authors may create three types of buttons:

• submit buttons: When activated, a submit button submits a form. A form may contain more than one submit button.
• reset buttons: When activated, a reset button resets all controls to their initial values.
• push buttons: Push buttons have no default behavior. Each push button may have client-side scripts associated with the element’s event attributes. When an event occurs (e.g., the user presses the button, releases it, etc.), the associated script is triggered.

  Authors should specify the scripting language of a push button script through a default script declaration (with the META element).

Authors create buttons with the BUTTON element or the INPUT element. Please consult the definitions of these elements for details about specifying different button types.

Note. Authors should note that the BUTTON element offers richer rendering capabilities than the INPUT element.

checkboxes

Checkboxes (and radio buttons) are on/off switches that may be toggled by the user. A switch is “on” when the control element’s checked attribute is set. When a form is submitted, only “on” checkbox controls can become successful.

Several checkboxes in a form may share the same control name. Thus, for example, checkboxes allow users to select several values for the same property. The INPUT element is used to create a checkbox control.

radio buttons

Radio buttons are like checkboxes except that when several share the same control name, they are mutually exclusive: when one is switched “on”, all others with the same name are switched “off”. The INPUT element is used to create a radio button control.

If no radio button in a set sharing the same control name is initially “on”, user agent behavior for choosing which control is initially “on” is undefined. Note. Since existing implementations handle this case differently, the current specification differs from RFC 1866 ([RFC1866] section 8.1.2.4), which states:

At all times, exactly one of the radio buttons in a set is checked. If none of the <INPUT> elements of a set of radio buttons specifies `CHECKED’, then the user agent must check the first radio button of the set initially.

Since user agent behavior differs, authors should ensure that in each set of radio buttons that one is initially “on”.

menus

Menus offer users options from which to choose. The SELECT element creates a menu, in combination with the OPTGROUP and OPTION elements.

text input

Authors may create two types of controls that allow users to input text. The INPUT element creates a single-line input control and the TEXTAREA element creates a multi-line input control. In both cases, the input text becomes the control’s current value.

file select

This control type allows the user to select files so that their contents may be submitted with a form. The INPUT element is used to create a file select control.

hidden controls

Authors may create controls that are not rendered but whose values are submitted with a form. Authors generally use this control type to store information between client/server exchanges that would otherwise be lost due to the stateless nature of HTTP (see [RFC2616]). The INPUT element is used to create a hidden control.

object controls

Authors may insert generic objects in forms such that associated values are submitted along with other controls. Authors create object controls with the OBJECT element.

The elements used to create controls generally appear inside a FORM element, but may also appear outside of a FORM element declaration when they are used to build user interfaces. This is discussed in the section on intrinsic events. Note that controls outside a form cannot be successful controls.

17.3 The FORM element

<!ELEMENT FORM - - (%block;|SCRIPT)+ -(FORM) -- interactive form -->
<!ATTLIST FORM
  %attrs;                              -- %coreattrs, %i18n, %events --
  action      %URI;          #REQUIRED -- server-side form handler --
  method      (GET|POST)     GET       -- HTTP method used to submit the form--
  enctype     %ContentType;  "application/x-www-form-urlencoded"
  accept      %ContentTypes; #IMPLIED  -- list of MIME types for file upload --
  name        CDATA          #IMPLIED  -- name of form for scripting --
  onsubmit    %Script;       #IMPLIED  -- the form was submitted --
  onreset     %Script;       #IMPLIED  -- the form was reset --
  accept-charset %Charsets;  #IMPLIED  -- list of supported charsets --
  >

Start tag: required, End tag: required

The FORM element acts as a container for controls. It specifies:

• The layout of the form (given by the contents of the element).
• The program that will handle the completed and submitted form (the action attribute). The receiving program must be able to parse name/value pairs in order to make use of them.
• The method by which user data will be sent to the server (the method attribute).
• A character encoding that must be accepted by the server in order to handle this form (the accept-charset attribute). User agents may advise the user of the value of the accept-charset attribute and/or restrict the user’s ability to enter unrecognized characters.

A form can contain text and markup (paragraphs, lists, etc.) in addition to form controls.

 <FORM action="http://somesite.com/prog/adduser" method="post">
 ...form contents...
 </FORM>

Please consult the section on form submission for information about how user agents must prepare form data for servers and how user agents should handle expected responses.

17.4 The INPUT element

<!ENTITY % InputType
  "(TEXT | PASSWORD | CHECKBOX |
    RADIO | SUBMIT | RESET |
    FILE | HIDDEN | IMAGE | BUTTON)"
   >

<!-- attribute name required for all but submit and reset -->
<!ELEMENT INPUT - O EMPTY              -- form control -->
<!ATTLIST INPUT
  %attrs;                              -- %coreattrs, %i18n, %events --
  type        %InputType;    TEXT      -- what kind of widget is needed --
  name        CDATA          #IMPLIED  -- submit as part of form --
  value       CDATA          #IMPLIED  -- Specify for radio buttons and checkboxes --
  checked     (checked)      #IMPLIED  -- for radio buttons and check boxes --
  disabled    (disabled)     #IMPLIED  -- unavailable in this context --
  readonly    (readonly)     #IMPLIED  -- for text and passwd --
  size        CDATA          #IMPLIED  -- specific to each type of field --
  maxlength   NUMBER         #IMPLIED  -- max chars for text fields --
  src         %URI;          #IMPLIED  -- for fields with images --
  alt         CDATA          #IMPLIED  -- short description --
  usemap      %URI;          #IMPLIED  -- use client-side image map --
  ismap       (ismap)        #IMPLIED  -- use server-side image map --
  tabindex    NUMBER         #IMPLIED  -- position in tabbing order --
  accesskey   %Character;    #IMPLIED  -- accessibility key character --
  onfocus     %Script;       #IMPLIED  -- the element got the focus --
  onblur      %Script;       #IMPLIED  -- the element lost the focus --
  onselect    %Script;       #IMPLIED  -- some text was selected --
  onchange    %Script;       #IMPLIED  -- the element value was changed --
  accept      %ContentTypes; #IMPLIED  -- list of MIME types for file upload --
  >