HTML Forms

Web Architecture [./]
Fall 2011 — INFO 253 (CCN 42598)

Dilan MahendranUC Berkeley School of Information, UC Berkeley School of Information
2011-10-13

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Contents D. Mahendran: HTML Forms

Contents

2Abstract
1 Forms Basics
- 4HTTP Web Services
- 5Forms Mechanics
- 6Forms Markup
- 7Forms Elements (User View)
- 8Forms Elements (Source View)
- 9Date Entry
- 10Forms and GET
- 11Forms and POST
- 12POST Form Processing
- 13Processing of Form Data
2 Structuring Forms
- 15Form Usability
- 16Labels
- 17Fieldsets
- 18Tabbing in Forms
- 19Disabled and Readonly Controls
- 20Disabled and Readonly Controls Display
- 21Markup for Disabled/Readonly Controls
22Conclusions

D. Mahendran: HTML Forms

(2) Abstract

This lecture introduces HTML Forms, a way how an HTML page can provide input fields, so that users can provide data to a Web-based application. HTML forms are regular HTML pages (i.e., using regular HTML structures), but they also contain special HTML elements for data entry. Most importantly, each form contains instructions on how to submit the entered data, and the browser will use that information to send an HTTP request containing all the data of the form submission.

Forms Basics

Outline (Forms Basics)

Forms Basics [10]
Structuring Forms [7]

Forms Basics D. Mahendran: HTML Forms

(4) HTTP Web Services

Services can be provided through URI/HTTP
- URI-based services need input as a query string
- the question is how the user gets information into the URI
HTML forms provide an interface for assembling query strings
- users fill out a form providing several fields
- the browser submits the entered information by HTTP to a URI
- the result of the request is displayed to the user
HTTP has two different methods for submitting data
- GET [Forms and GET (1)] encodes the data as a URI query string
- POST [Forms and POST (1)] encodes the data as HTTP request entity

Forms Basics D. Mahendran: HTML Forms

(5) Forms Mechanics

HTML forms are normal Web pages (using form elements)
The process receiving the form data produces a result page

Forms Basics D. Mahendran: HTML Forms

(6) Forms Markup

All form elements must be inside a form element
- specifies the URI for submitting the form values (action="URI")
- specifies the method for submitting the form values (method="GET [Forms and GET (1)]|POST [Forms and POST (1)]")
form contains regular HTML markup and form elements
- the regular HTML markup creates the form's layout (table, list, texts)
- the form elements create the controls for acquiring input data
Each form should have a submit button
- when pressing this button, the form values are sent to the action URI
- without such a button, the form values cannot be submitted

Forms Basics D. Mahendran: HTML Forms

(7) Forms Elements (User View)

HTML provides a small set of form controls
Sufficient for many applications

Forms Basics D. Mahendran: HTML Forms

(8) Forms Elements (Source View)

<form action="http://stevex.net/dump.php" method="POST" enctype="multipart/form-data"><table>
	<tr><td>Text:</td><td><input type="text" name="text" value="text input"/></td></tr>
	<tr><td>Password:</td><td><input type="password" name="password" value="hidden text"/></td></tr>
	<tr><td>Checkbox:</td><td><input type="checkbox" name="check" value="1"/> <input type="checkbox" name="check" value="2"/> <input type="checkbox" name="check" value="3"/></td></tr>
	<tr><td>Radio Button:</td><td><input type="radio" name="radio" value="1"/> <input type="radio" name="radio" value="2"/> <input type="radio" name="radio" value="3"/></td></tr>
	<tr><td>Text Areas:</td><td><textarea name="textarea" rows="2" cols="20"/></td></tr>
	<tr><td>Selection:</td><td><select name="select"><option selected="selected">XML</option><option>SGML</option></select></td></tr>
	<tr><td>Multiple Selection:</td><td><select name="mselect" multiple="multiple"><option>242</option><option>290-3</option><option>290-13</option></select>
	<tr><td>File Upload:</td><td><input name="file" type="file"/></td></tr>
	<tr><td valign="top" align="right">Hidden:</td><td><input type="hidden" name="hidden" value="hidden input"/></td></tr>
	<tr><td>Submit:</td><td><input name="submit" type="submit"/></td></tr>
</table></form>

Forms Basics D. Mahendran: HTML Forms

(9) Date Entry

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
 <head>
  <title>JavaScript Datepicker</title>
  <script type="text/javascript" src="date-picker.js"></script>
  <link rel="stylesheet" type="text/css" href="date-picker.css">
 </head>
 <body>
  <form action="http://stevex.net/dump.php" method="GET">
   <input type="text" name="date">
   <input type="button" value="calendar" onclick="displayDatePicker('date');">
   <input type="submit" value="submit date">
  </form>
 </body>
</html>

date-picker.html

Forms Basics D. Mahendran: HTML Forms

(10) Forms and GET

Limited to string-oriented form values
- but HTML forms also allow file upload (this requires POST)
All values of all form input fields are collected
- for text and selection fields, this is one input field
- for checkboxes and radio buttons, this collects the selected fields
The browser composes a URI query string
- the form submission is a set of name/value pairs (names may appear more than once!)
- using URI query string notation, it is appended to the URI of the form's action
GET is good!
- URI-encoded queries can be bookmarked and otherwise reused (e.g., cached)
- if possible, use GET when implementing a form

Forms Basics D. Mahendran: HTML Forms

(11) Forms and POST

GET encodes the values in the URI
- for file uploads, this is not possible
- HTTP's POST request method can upload data
POST sends a request containing an entity
- the HTTP request then looks similar to a response (header fields and entity)
- the receiving process (the Web server) accepts the POST body
Entities can use any format (it is specified in a header field)
- just like e-mails, entities can have multiple parts
- the parts are separated using the standard MIME mechanism

Forms Basics D. Mahendran: HTML Forms

(12) POST Form Processing

POST is used if the form specifies it
- it can (but should not) be used for non-file forms
- it should be used for file upload forms (otherwise, only the name is uploaded)
File upload forms must specify the appropriate encoding
- application/x-www-form-urlencoded is the default (values in the entity)
- multipart/form-data is required for file upload (multipart form data)
The server side must be prepared to receive POST requests
- it must parse the entity rather than the URI's query string
- form values can then be extracted from the entity
- some environments (e.g., PHP) allow to handle GET/POST transparently

Forms Basics D. Mahendran: HTML Forms

(13) Processing of Form Data

Form data is always encoded
- as a query string when using GET
- in an encoded entity when using POST
- in a multipart entity when using POST with multipart/form-data
Parsing the form data should be done by existing software
- most Web-aware programming environments provide this functionality
- PHP allows access through different mechanisms

  <p>Query Parameter Test:</p>
  <p>test: <?php echo $_REQUEST["test"]; ?></p>
  <p>name: <?php echo $_REQUEST["name"]; ?></p>
  <p>field: <?php echo $_REQUEST["field"]; ?></p>

form-variables.php (line 8-11)

Structuring Forms

Outline (Structuring Forms)

Forms Basics [10]
Structuring Forms [7]

Structuring Forms D. Mahendran: HTML Forms

(15) Form Usability

HTML forms are very loosely structured
- form somewhere representing the container
- inside the form a random collection of HTML and form inputs
Visually, the structure often is (and should be) easy to see
- for non-visual access, more structure must be provided
- accessibility has become a major issue on the Web
Accessibility has many different facets
- voice browsers must be able to read aloud Web forms
- gateways should be able to intelligently re-structure Web forms

Structuring Forms D. Mahendran: HTML Forms

(16) Labels

Label and form control are not connected by HTML

<tr><td>Text:</td><td><input type="text" name="text"/></td></tr>
<tr><td>Password:</td><td><input type="password" name="password"/></td></tr>

The label element allows this connection be made
- it connects a form control with the describing label
- this association is now accessible to clients for processing

<tr>
 <td><label for="textctrl">Text:</label></td>
 <td><input type="text" name="text" id="textctrl"/></td>
 </tr>
 <tr>
 <td><label for="pwdctrl">Password:</label></td>
 <td><input type="password" name="password" id="pwdctrl"/></td>
</tr>

Structuring Forms D. Mahendran: HTML Forms

(17) Fieldsets

Complex forms may need structuring
- groups of controls for subsets of the collected data
- this structure should be represented in markup

<fieldset><legend>Billing</legend>billing form HTML …</fieldset>
<fieldset><legend>Shipping</legend> shipping form HTML … </fieldset>

Excellent example for HTML's markup design philosophy
- if a client does not support fieldsets, the elements are ignored
- the title of the fieldset will be displayed, because it is text

Billingbilling form controls …

Shippingshipping form controls …

Structuring Forms D. Mahendran: HTML Forms

(18) Tabbing in Forms

Tabbing is a very convenient way of navigating a form
- after completing one field, users should be taken to the next
- the order should be defined by the form creator, not by accident
the tabindex attribute defines the tabbing order
- it contains a number which is interpreted relative to other numbers
- all form controls may carry a tabindex attribute
tabindex 1-9:

Structuring Forms D. Mahendran: HTML Forms

(19) Disabled and Readonly Controls

In complex scenarios, certain controls may be disabled or readonly
- based on a workflow, some controls may not apply in all cases
- for the sake of a consistent view, they should still be included in the interface
Disabled controls are not used
- they cannot be tabbed to and never receive focus
- their value is not included in the form's submission data
Readonly controls cannot be changed
- they can be tabbed to and may receive focus
- their value may not be changed (important for radio buttons and checkboxes!)
- their value is included in the form's submission data
Important: Never trust the Browser!

Structuring Forms D. Mahendran: HTML Forms

(20) Disabled and Readonly Controls Display

	Normal Control	Disabled Control	Readonly Control
Text:
Password:
Checkbox:			!
Radio Button:			!
File Upload:			!
Text Areas:	initial text	initial text	initial text
Selection:			[ not supported ]
Multiple Selection:			[ not supported ]

Structuring Forms D. Mahendran: HTML Forms

(21) Markup for Disabled/Readonly Controls

   <table style="margin : 2% ; width : 90% ; " rules="groups" cellpadding="5">
    <thead><tr>
     <td></td>
     <th>Normal Control</th>
     <th>Disabled Control</th>
     <th>Readonly Control</th>
    </tr></thead>
    <tbody>
     <tr><td valign="top" align="right">Text:</td><td><input type="text" name="text1" value="text input"></td><td><input disabled="disabled" type="text" name="text2" value="text input"></td><td><input readonly="readonly" type="text" name="text3" value="text input"></td></tr>
     <tr><td valign="top" align="right">Password:</td><td><input type="password" name="password1" value="hidden text"></td><td><input disabled="disabled" type="password" name="password2" value="hidden text"></td><td><input readonly="readonly" type="password" name="password3" value="hidden text"></td></tr>
     <tr><td valign="top" align="right">Checkbox:</td><td><input type="checkbox" name="check1" value="1"> <input type="checkbox" name="check1" checked="checked" value="2"> <input type="checkbox" name="check1" value="3"></td><td><input disabled="disabled" type="checkbox" name="check2" value="1"> <input disabled="disabled" type="checkbox" name="check2" checked="checked" value="2"> <input disabled="disabled" type="checkbox" name="check2" value="3"></td><td><input readonly="readonly" type="checkbox" name="check3" value="1"> <input readonly="readonly" type="checkbox" name="check3" checked="checked" value="2"> <input readonly="readonly" type="checkbox" name="check3" value="3"> !</td></tr>

forms.html (line 9-19)

D. Mahendran: HTML Forms

(22) Conclusions

HTML forms allow data entry on Web pages
Only a small number of form controls are available
Form submission is just another HTTP request
Forms should be structured to be more accessible

2011-10-13 Web Architecture [./]
Fall 2011 — INFO 253 (CCN 42598)