Transcript Document

XP
New Perspectives on Creating Web Pages
with HTML
Tutorial 6: Creating Web Page Forms
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Tutorial Objectives
•
•
•
•
•
•
Learn about CGI scripts
Review the various parts of an online form
Create form elements
Create a hidden field on a form
Work with form attributes
Learn how to send data from a form to a CGI
script
• Learn how to send form information without using
CGI scripts
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An Example of a Form
This figure shows
a sketch of a
proposed
registration form.
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The Interaction between a XP
Web Page Form and a CGI Script
This figure shows
how a Web page
form interacts
with a CGI script.
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Working with CGI Scripts
• HTML supports tags for creating forms, however, it does
not process the information.
• Use CGI (Common Gateway Interface) script to process
form information.
• CGI script runs on the Web server and receives data from a
form and uses it to perform a set of tasks.
• Web page designers may not be able to create or edit CGI
scripts.
– Internet Service Providers (ISPs) and universities may provide CGI
scripts that their customers and student can use on their Web sites,
but which they cannot directly access or modify
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CGI Scripts
• Among the many things CGI scripts made possible are:
–
–
–
–
online database containing customer information
catalogues for ordering and purchasing items online
databases containing product support information
determining the number of times a Web page has been
accessed
– server-side image maps
– message boards for online discussion forums
– e-mail for discussion groups
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CGI Script Restrictions
• There are several reasons to restrict direct access to CGI
scripts:
– CGI scripts are actually running a program directly on the
server
– security risks from computer hackers
– drain on system resources caused by large numbers of
programs running simultaneously
• System administration are understandably careful to
maintain strict control over their servers and systems.
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CGI Scripts and Computer Languages
• CGI scripts can be written in a variety of different computer
languages. Some of the most commonly used languages are:
–
–
–
–
–
–
–
AppleScript
ASP
C/C++
Perl
TCL
The UNIX shell
Visual Basic
• The computer language used depends on the Web server.
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Form Components and Elements
text box
This figure shows
a form that
contains various
control elements
commonly used in
Web page forms. drop-down
First Name
Last Name
Address #1
Address #2
State
City
Zip
Country
Item Purchased
Purchase Date
group
box
Serial Number
list box
Used For (check one)
radio
buttons
Home
Business
Religious or Charitable Institution
Government
Educational Institution
Network Operating System (check all that apply)
Netware
Banyan Vines
Windows
IBM Lan Server
PC/NFS
Comments?:
form
button
Send Registration
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check
boxes
text
area
Cancel
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Form Control Elements
• Control elements that are commonly used:
– text boxes for text and numerical entries
– selection lists for long lists of options, usually appearing in a
drop-down list box
– radio buttons, also called option buttons, to select a single
option from a predefined list
– check boxes to specify an item as either present or absent
– groups boxes to organize form elements
– text areas for extended entries that can include several lines
of text
– buttons that can be clicked to start processing the form
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Form Control Elements Continued
• Each control element in which the user can enter
information is called a field.
• Information entered into a field is called the field value, or
simply the value.
• In some fields, users are free to enter anything they choose.
• Other fields, such as selection lists, limit the user to a
predefined list of options.
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The <form> Tag
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• The <form> tag identifies the beginning and end of a form.
• A single page can include several different forms, but you
cannot nest one form inside another.
• The general syntax of the <form> tag is:
<form attributes>
form elements and layout tags
</form>
• Between the <form> and </form> tags, place the various
tags for each of the fields in the form.
• Use standard HTML tags to specify the form’s appearance.
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The <form> Tag Continued
• A single Web page can contain multiple forms, the
<form> tag includes the name attribute.
• The name attribute identifies each form on the page.
• The name attribute is also needed for programs that
retrieve values from the form.
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Adding the <form> Tag
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The <form> tag
includes attributes
that control how the
form is processed,
including
information on what
CGI script to use,
how the data is to be
transferred to the
script, and so forth.
This figure shows the
form name “reg.”
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Structuring a Form
• Horizontal lines can provide structure to a form by
separating sections.
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Layout of a Registration Form
This figure shows sections that are separated from each other with a horizontal line.
Structuring a form in this fashion can make it easier to identify the different sections.
contact information
product information
usage information
comments
buttons
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Input Types
This figure
shows other
supported
HTML input
types.
Type
Description
type=”button”
Display a button which can be clicked to
perform an action from a script
type=”checkbox”
Display a check box
type=”file”
Display a browse button to locate and select a
file
type=”hidden”
Create a hidden field, not viewable on the form
type=”image”
Display an inline image which can be clicked to
perform an action from a script
type=”password”
Display a text box in which hides text entered
by the user
type=”radio”
Display a radio (option) button
type=”reset”
Display a button which resets the form when
clicked
type=”submit”
Display a button which submits the form when
clicked
type=”text”
Display a text box in which displays text
entered by the user
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Working with Text Boxes
• Text boxes are created using the <input> tag.
• The general syntax is:
<input type=“type” name=“name” id=“id”>
– type specifies the type of input field
– name and id attributes identifies the input field for the CGI
script
• To create a text box, you would enter the tag:
<input type=“text”>
• If the type attribute is not included, the Web browser
assumes, by default, that you want to create a text box.
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The name and id Attribute
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• The name and id attributes of the <input> tag identifies
the input field for the CGI script.
• The name attribute represents the older standard, but it is
deprecated in HTML 4.01, however, some CGI scripts still
recognize only the name attribute
• The newest standard uses the id attribute.
• The id attribute is required, if a form contains form labels.
• It is best to duplicate the information by using both the
name and id attributes.
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Creating a Text Box
• To create a text box, use the following HTML code:
<input name=“name” id=“id” value=“value”
size=“value” maxlength=“value”>
– name and id attributes identify the field
– value attribute assigns a default value to the text box
– size attribute defines the width of the text box in number
of characters
– maxlength attribute defines the maximum number of
characters allowed in the field
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Name/Value Pairs sent from XP
the Web Form to the CGI Script
This figure shows
when form data is
sent to the CGI
script, the script
receives the name
or id of each field
in the form
paired with
whatever value
the user entered
in the field. The
script then
processes the data
according to each
name/value pair.
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CGI Script Names
• Some CGI scripts require a particular field or groups of
fields.
– for example, a CGI script whose purpose is to e-mail form
values to another user might require a field named “email”
that contains the e-mail address of the recipient
• Before using a CGI script, check the documentation for
any requirements and then design your form accordingly.
• Case is important in field names.
– a field named “email” might not be interpreted by the CGI
script in the same way as a field named “EMAIL”
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Text Boxes on the Form
Text boxes are
blank and do
not contain any
accompanying
text, a text
description
needs to be
inserted, such as
“Last Name”,
adjacent to each
box so that the
user knows what
to enter.
text box
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Controlling the Size of a Text Box
• By default, all text boxes are 20 characters wide.
• The syntax for changing the size of a text box is:
<input size=“value”>
– value is the size of the text box in characters
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Setting the Width of Text Boxes
This figure
shows an
example of code
for setting the
width of text
boxes.
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Result of Setting the
Width of Text Boxes
Once changes
are made, save
the changes to a
file, and then
reload or refresh
it in the browser.
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text box width set to
30 characters
Netscape users
may have to
close and open
the file for the
changes to the
Web form to
take effect.
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Setting the Maximum Length
for Text Input
• Setting the width of a text box does not limit the number of
characters the box can hold.
– if a user enters text longer than the box’s width, the text scrolls
to the left
– the user cannot see the entire text, but all of it is sent to the
CGI script for processing
• The syntax for setting the maximum length for field input is:
<input maxlength=“value”>
– value is the maximum number of characters that can be stored
in the field
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Specify the Maximum Length
for a Field
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This figure shows an example of limiting the width of the zip code field to five characters.
no more than 5
characters are
allowed in this text
box
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Setting a Default Value for a Field
• When the same value is entered into a field, it may
make sense to define a default value for a field.
• Default values can save time and increase
accuracy for users of a Web site.
• To define a default value, use the following
syntax:
<input value=“value”>
– value is the default text or number that is displayed in
the field
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Defining a Default Value for a Field
If customers from countries other than the United States use this Web form,
they can remove the default value by selecting the text and pressing the Delete key.
default value
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Creating a Password Field
• A password field is a text box in which the characters
typed by the user are displayed as bullets or asterisks i.e.
****.
• The syntax for creating a Password field is:
<input type=“password”>
• Using a password field should not be confused with having
a secure connection.
• The password itself is not encrypted.
• The password field only acts as a mask for a field entry as
it is entered.
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Working with Form Labels
• HTML allows you to formally link a label with an
associated text element for scripting purposes.
• The syntax for creating a form label is:
<label for=“id”>label text</label>
– id is the value of the id attribute for a field on the form
– label text is the text of the label
– you must bind the label to the id attribute of the field and not
the name attribute
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Working with Form Labels
• Labels can simplify the data entry process by allowing a
user to click on either the control element or the element’s
label to enter data.
• Labels allow users to write scripts to modify their content
for interactive forms.
• The <label> tag is part of the HTML 4.0 specifications,
however, it is not currently supported by Netscape.
• The Netscape browser, and versions of the Internet
Explorer browser prior to 4.0, ignore the <label> tag,
but still display the label text.
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Creating a Label for the fname Field
This figure shows
a label for the
fname field.
value of the id
attribute for the first
name field
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Creating a Selection List
• A selection list is a list box from which a user selects a
particular value or set of values.
• Selection lists are good to use when there is a fixed set of
possible responses.
• Selection lists help prevent spelling mistakes and
erroneous entries.
• A selection list is created using the <select> tag.
• The <option> tag is used to specify individual selection
items.
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Creating a Selection List
This figure shows
HTML code for
creating a
selection list.
selection list field
name
items in the selection
list
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Using a Selection List
Your selection
list might look
slightly different
depending on the
browser and
browser version.
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Using the <select>
and <option> Tags
• The general syntax for the <select> and <option> tags is:
<select name=“name” id=“id”>
<option> item1
<option> item2
.
.
.
</select>
– name and id attribute identify the selection field
– each <option> tag represents an individual item in the selection
list
– the text in the selection list is indicated by the text in item1, item2,
and so forth
• The <option> tag is a one-sided tag.
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Modifying the Appearance
of a Selection List
• HTML provides several attributes to modify the
appearance and behavior of selection lists and options.
• By default, the <select> tag displays one option from
the selection list, along with a list arrow to view additional
selection options.
• The number of options displayed can be modified with the
size attribute.
• The syntax of the size attribute is:
<select size=“value”>
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Modifying the Appearance
of a Selection List Continued
– value is the number of items that the selection list
displays in the form
– by specifying a value greater than 1, the selection list
changes from a drop-down list box to a list box
– if the size attribute is equal to the number of options in
the selection list, the scroll bar is either not displayed or
is dimmed
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Selection Lists with
Different Size Values
This figure shows
selection lists with
different size
values.
size = "1"
size = "7"
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size = "4"
size = "9"
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Making Multiple Selections
• When using multiple selections, users are not limited to a
single selection from a selection list.
• Adding the multiple attribute to the <select> tag allows
multiple selections from a list.
• The syntax for this attribute is:
<select multiple>
• A common method to make multiple selections from a
selection list is to hold down a specific key while making
selections.
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Making Multiple Selections Continued
• The Windows operating system, multiple selections can be
made as follows:
– for noncontiguous selections, press and hold the Ctrl key
while you make your selections
– for a contiguous selection, select the first item, press and
hold the Shift key, and then select the last item in the range
• Check and verify that the CGI scripts used are designed to
handle multiple selection lists.
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Working with Option Values
• By default, a form sends the values that are displayed
in the selection list to the CGI script.
• Instead of sending an entire text string, an
abbreviation or code can be sent to the CGI script.
• Specify the value that is sent to the CGI script with the
value attribute.
• Use the selected attribute to specify which item in the
selection is selected, or highlighted, when the form is
displayed.
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Working with Option Groups
• The most recent releases of HTML allows you to
organize selection lists into distinct groups called
option groups.
• The syntax for creating an option group is:
<optgroup label=“label”>
– label is the label assigned to the option group
– the text for the label appears in the selection list above
each group of items but is not a selectable item from the
list
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Option Groups
Internet Explorer and Netscape versions prior to 6.0 display
the selection list without the group labels.
option group
label
a single
option
group
option
group label
a single option
group
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Working with Radio Buttons
• Radio buttons display a list of choices from which a user
makes a selection.
• Only one radio button can be selected at a time.
• The syntax to create a radio button is:
<input type=“radio” name=“name” id=“id”
value=“value”>
– name identifies the field containing the radio button
– id attribute identifies the specific option. Only required if you
intend to use a field label with the radio button
– value attribute indicates the value sent to the CGI script, if that
radio button is selected by the user
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Working with
Radio Buttons Continued
• The name attribute must be included, because it
groups distinct radio buttons together.
– selecting one radio button in the group automatically
deselects all of the other radio buttons in that group
• Insert descriptive text next to the button.
• Enclose text within a label tag to allow the user to
select the radio button or label.
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Creating Radio Buttons
This figure shows an example of HTML code that creates radio buttons for party affiliations.
In this sample code, the value sent to the CGI script does not match the field label.
If the user selects the Republican radio button, the value “gop”
is sent to the CGI script paired with the field name “party.”
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Selection Lists vs. Radio Buttons
• If you have a long list of options, use a selection
list.
• If you want to allow users to select more than one
option, use a selection list with the multiple
attribute.
• If you have a short list of options, and only one
option is allowed at a time, use radio buttons.
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Creating a Group Box
• A group box labels an entire collection of radio
buttons.
• A group box is a box placed around a set of fields
that indicates that they belong to a common group.
• The syntax for creating a group box is:
<fieldset>
<legend align=“align”>legend
text</legend>
collection of fields
</fieldset>
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Creating a Group Box Continued
– the <legend> tag is used to display a legend on the group
box
– legend text specifies the text for that legend
– the align attribute specifies where the legend is placed in the
box
• align values are “top” (the default), “bottom”, “left”,
and “right”
• browsers only support “top” and “right” options at this
time
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Creating a Group Box and Legend
This figure shows
an example of a
group box applied
to a set of radio
buttons.
start of
group box
group box
legend
resulting radio buttons and group box
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Group Box Size
• There is no attribute to control the size of a group box.
• The box’s height will be large enough to accommodate the
fields and labels in the field set.
• The width is the width of whatever space remains on the
Web page.
• To set the width to a specific value use a table cell to place
the group box and set the width of the cell.
– group boxes cannot extend across table cells; all of the fields
in the field set must be placed within a single cell
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Working with Check Boxes
• A check box is either selected or not, there is only one check box
per field.
• Check boxes are created using the following syntax:
<input type=“checkbox” name=“name” id=“id”
value=“value”>
– name and id attribute identify the check box
– the value attribute specifies the value that is sent to the CGI script
when the check box is selected
• The <input> tag for a check box does not display any text.
• Check boxes are not selected by default.
– to do this, add the checked attribute to the <input> tag
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Adding Check Boxes
This figure shows different check boxes. The user can click either the check box or
the label associated with the check box to select and deselect.
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Group Boxes for Radio Buttons XP
and Check Boxes
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Creating a Text Area
• To create a larger text area for a text box, use the
tag:
<textarea name=“name” id=“id” rows=“value”
cols=“value”> default text </textarea>
– rows and cols attributes define the dimensions of the text
box
– the rows attribute indicates the number of lines in the text
box
• Default text can be specified in the text box when
the form is initially displayed.
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Creating a Text Area
This figure shows an
example of a text
area with default
text.
The <textarea>
tag is a two-sided tag,
which means that it
has an opening tag
<textarea>, and a
closing tag,
</textarea>.
default text
area text
dimensions
of text area
resulting text area
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Wrap Attribute Values
The text entered in a text area wraps to the next line when it exceeds the width of the
box. To control how a browser wraps text to a new line use the wrap attribute.
This figure shows the three possible wrap options.
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The wrap Attribute for Text
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• Set the value of the wrap attribute to either “soft” or
“hard” to allow text to wrap within the text box.
– the “hard” setting preserves any line wrapping that takes place in
the text box and the “soft” setting does not.
• If no value for the wrap attribute is specified, a value of
“soft” is used.
• For comment fields, use the <textarea> tag with the
wrap attribute set to “soft” so that the user’s comments
wrap to the next line in the box.
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Comment Text Area
In this figure the
text box includes a
vertical scroll bar,
so that a user can
scroll to see the
hidden text, if
needed.
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Creating Form Buttons
• Another type of control element is one that
performs an action. In forms, this is usually done
with a button.
• Buttons can be clicked to:
– run programs
– submit forms
– reset the form to its original state
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Creating a Push Button
• One type of button, called a push button, is
created using the <input> tag as follows:
<input type=“button” value=“text”>
– text is the text that appears on the button
• By themselves, push buttons perform no actions in
the Web page.
• To create an action, write a script or program that
runs automatically when the button is clicked.
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Creating Submit and Reset Buttons
• A submit button is a button that submits the form
to the CGI script for processing.
• A reset button resets the form to its original
(default) values.
• The syntax for creating these two buttons is:
<input type=“submit” value=“text”>
<input type=“reset” value=“text”>
– value attribute defines the text that appears on the
button
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The name and value Attributes
• The name and value attributes can be used for
push, submit, and reset buttons.
• Use these attributes when the form contains
multiple buttons and a program that processes the
form needs to distinguish one button from another.
– for example, a Web page advertising a shareware
program might include three buttons:
• one used to download the program
• another used to retrieve information
• the third to cancel the form
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Creating a Form Button
The figure shows HTML tags for buttons that download a program,
retrieves information, and resets the form to its original values.
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Creating Buttons
with the <button> Tag
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• Buttons created with the <input> tag do not allow the Web page
designer to control the appearance of the button.
• For greater artistic control over the appearance of the button, use the
<button> tag.
• The syntax of the <button> tag is:
<button name=“name” value=“value”
type=“option”>
button text and HTML tags
</button>
– name attribute specifies the name of the button
– value attribute sends to a CGI script
– type attribute specifies the button type (submit, reset, or button)
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Using the <button> Tag
The figure shows how
to create a button that
contains formatted
text and an inline
image.
The default value for
the type attribute is
“button”. Within the
<button> tags you
can place whatever
HTML tags you wish
to format the button’s
appearance. This
includes inline
images.
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the button type is a
simple push button
contents
of the
button
button image
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Creating File Buttons
• A file button is used to select files so that their
contents can be submitted for processing to a CGI
script.
• The contents of the file are not displayed--only the
file’s location.
• A programmer can then use that information to
retrieve a file and use it for whatever purpose is
required by the script.
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Using a File Button
The figure shows
an example of
using the file
button to return
the location of a
file named
“report.doc.”
1. User clicks the Browse button
2. Selects a file from the
Choose File dialog box
3. The filename and location
are automatically placed in
the text box
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Creating Image Fields
• Inline images can act like submit buttons, so that when the user clicks the
image, the form is submitted.
• The syntax for this type of control element is:
<input type=“image” src=“URL” name=“text”
value=“text”>
– URL is the filename and location of the inline image
– name attribute assigns a name to the field
– value attribute assigns a value to the image
• When the form is submitted to the CGI script, the coordinates of where the
user clicked are attached to the image’s name and value in the format:
namex_coordinate, value.y_coordinate.
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Using an Image Control
with a CGI Script
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Once the CGI
script receives
data, the action it
performs depends
on whether the
user clicked
within the image.
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Working with Hidden Fields
• A hidden field is added to the form but not displayed in the
Web page.
• Because the field is hidden, it can be placed anywhere
between the opening and closing <form> tags.
• The syntax for creating a hidden field is:
<input type=“hidden” name=“name”
value=“value>
• Place all hidden fields in one location to make it easier to
read and interpret the HTML code.
• Include a comment describing the purpose of the field.
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Adding a Hidden Field
This figure shows
an example of the
hidden field code.
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Working with Form Attributes
• To specify where to send the form data and how to
send it add the following attributes to the <form>
tag:
<form action=“URL” method=“option”
enctype=“text”>
– URL specifies the filename and location of the CGI script
that process the form
– method attribute specifies how your Web browser sends data
to the CGI script
– enctype attribute specifies the format of the data stored in the
form’s field
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The method Attribute
• There are two possible values for the method attribute: “get” or
“post”.
– the “get” method (the default) packages the form data by
appending it to the end of the URL specified in the action attribute
– the “post” method sends form data in a separate data stream,
allowing the Web server to receive the data through what is called
“standard input”
– the “post” method is considered the preferred way of sending data
to a Web server
– The “post” method is also safer, because some Web servers limit
the amount of data sent via the “get” method and will truncate the
URL, cutting off valuable information
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The enctype Attribute
• The exact meaning of the enctype attribute is a technical
issue.
• The default enctype value is “application/x-www-formurlencoded.”
• Another enctype value that is often used is
“multipart/form-data,” which allows the form to send
files to the Web server along with any form data.
• The most basic way of encoding data is to use
“text/plain,” which encodes the data as simple text.
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Specifying Where and How
to Send Form Data
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This figure shows the CGI script that processes the form is located at the URL
http://www.langear.com/cgi/mailer (a fictional address) and uses the “post” method.
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Form Values
The Web browser
presents a page, an
example of which is
shown in this figure,
displaying the name
of each field in the
form and the value
assigned to it. At the
same time, the CGI
script formats a mail
message to be sent to
the address you
entered.
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Using the “mailto” Action
• Use the “mailto” action to send form information via email without using a CGI script.
• This action accesses the user’s own e-mail program and uses
it to mail form information to a specified e-mail address,
bypassing the need for using CGI scripts on a Web server.
• The syntax of the “mailto” action is:
<form action=“mailto:e-mail_address”
method=“post” enctype=“text/plain”>
– e-mail_address is the e-mail address of the recipient of
the form
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Using the “mailto”
Action Continued
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• Not all browsers support the “mailto” action.
– for example, versions of Internet Explorer earlier than
4.0 and Netscape Navigator 3.0 do not
• Another concern is that messages sent via the
“mailto” action are not encrypted for privacy.
• The recipient’s email address is revealed to the user.
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Mail Message Created Using
the “mailto” Action
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This figure shows an
e-mail message that
the “mailto” action
generated for a
registration form.
The format of the
mail message may
look different
depending on the
browser or e-mail
software.
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Specifying the Tab Order
• Users navigate through a Web form using the Tab key.
– the Tab key moves the cursor from one field to another in the order
that the field tags are entered.
• Add the tabindex attribute to any control element in the
form to specify the tab order.
• With each element assigned a tab index number, the cursor
moves through the fields from the lowest index number to
the highest.
– for example, to assign the tab index number “1” to the fname field,
enter the code: <input name=“fname” tabindex=“1”>
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Tab Order and Browsers
• Browsers that do not support the tab order feature
simply ignores the tabindex attribute and
continues to tab to the fields in the order that they
appear in the HTML code.
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Specifying an Access Key
• An access key is a single key that you type in conjunction
with the Alt key for Windows users or the Command key for
Macintosh users, to jump to one of the control elements in the
form.
• Add the accesskey attribute to any of the control elements to
create an access key.
• To create an access key for the lname field, enter the
following code: <input name=“lname”
accesskey=“1”>
– if a user types Alt+l (or Command+1 for Macintosh users), the control
element for the lname field is selected
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Specifying an Access Key Continued
• Use letters that are not reserved by the browser.
– for example, Alt_f is used by Internet Explorer to access the File
menu
• When an access key is used, provide some visual clue about
the key’s existence.
– the accepted method is to underline the character corresponding
to the access key. For example, “Last Name”
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Tutorial 6 Summary
•
•
•
•
•
•
•
Worked with Web page forms.
Overview of scripts.
CGI scripts.
Created simple input boxes.
Worked with properties.
Controlled the appearance of input boxes.
Worked with Web form elements and components.
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Tutorial 6 Summary Continued
• Controlled the appearance and behavior of various
elements.
• Examined form buttons, form images and hidden
fields.
• Focused on how information is transferred from
the Web page form to the CGI script.
• Worked with various form actions and methods.
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