CGI::HTML::Functions(3) User Contributed Perl Documentation
NAME
CGI::HTML::Functions - Documentation for CGI.pm Legacy HTML Functionality
SYNOPSIS
Nothing here - please do not use this functionality, it is considered to
be legacy and essentially deprecated. This documentation exists solely to
aid in maintenance and migration of legacy code using this functionality
and you are strongly encouraged to migrate away from it. If you are
working on new code you should be using a template engine. For more
information see CGI::Alternatives.
If you really want to continue using the HTML generation functionality of
CGI.pm then you should take a look at HTML::Tiny instead, which may give
you a migration path away from CGI.pm's html generation functions; i
strongly encourage you to move towards template driven page generation
for anything involving markup as it will make porting your app to other
frameworks much easier in the long run.
DESCRIPTION
The documentation here should be considered an addendum to the sections
in the CGI documentation - the sections here are named the same as those
within the CGI perldoc.
Calling CGI.pm routines
HTML tag functions have both attributes (the attribute="value" pairs
within the tag itself) and contents (the part between the opening and
closing pairs). To distinguish between attributes and contents, CGI.pm
uses the convention of passing HTML attributes as a hash reference as the
first argument, and the contents, if any, as any subsequent arguments.
It works out like this:
Code Generated HTML
---- --------------
h1() <h1 />
h1('some','contents'); <h1>some contents</h1>
h1({-align=>left}); <h1 align="LEFT">
h1({-align=>left},'contents'); <h1 align="LEFT">contents</h1>
Many newcomers to CGI.pm are puzzled by the difference between the
calling conventions for the HTML shortcuts, which require curly braces
around the HTML tag attributes, and the calling conventions for other
routines, which manage to generate attributes without the curly brackets.
Don't be confused. As a convenience the curly braces are optional in all
but the HTML shortcuts. If you like, you can use curly braces when
calling any routine that takes named arguments. For example:
print $q->header( { -type => 'image/gif', -expires => '+3d' } );
If you use warnings, you will be warned that some CGI.pm argument names
conflict with built-in perl functions. The most frequent of these is the
-values argument, used to create multi-valued menus, radio button
clusters and the like. To get around this warning, you have several
choices:
1. Use another name for the argument, if one is available. For example,
-value is an alias for -values.
2. Change the capitalization, e.g. -Values
3. Put quotes around the argument name, e.g. '-values'
Function-oriented interface HTML exports
Here is a list of the HTML related function sets you can import:
:form
Import all fill-out form generating methods, such as textfield().
:html2
Import all methods that generate HTML 2.0 standard elements.
:html3
Import all methods that generate HTML 3.0 elements (such as <table>,
<super> and <sub>).
:html4
Import all methods that generate HTML 4 elements (such as <abbrev>,
<acronym> and <thead>).
:netscape
Import the <blink>, <fontsize> and <center> tags.
:html
Import all HTML-generating shortcuts (i.e. 'html2', 'html3', 'html4'
and 'netscape')
:standard
Import "standard" features, 'html2', 'html3', 'html4', 'ssl', 'form'
and 'cgi'.
If you import any of the state-maintaining CGI or form-generating
methods, a default CGI object will be created and initialized
automatically the first time you use any of the methods that require one
to be present. This includes param(), textfield(), submit() and the like.
(If you need direct access to the CGI object, you can find it in the
global variable $CGI::Q).
Pragmas
Additional HTML generation related pragms:
-nosticky
By default the CGI module implements a state-preserving behavior
called "sticky" fields. The way this works is that if you are
regenerating a form, the methods that generate the form field values
will interrogate param() to see if similarly-named parameters are
present in the query string. If they find a like-named parameter,
they will use it to set their default values.
Sometimes this isn't what you want. The -nosticky pragma prevents
this behavior. You can also selectively change the sticky behavior in
each element that you generate.
-tabindex
Automatically add tab index attributes to each form field. With this
option turned off, you can still add tab indexes manually by passing
a -tabindex option to each field-generating method.
-no_xhtml
By default, CGI.pm versions 2.69 and higher emit XHTML
(http://www.w3.org/TR/xhtml1/). The -no_xhtml pragma disables this
feature. Thanks to Michalis Kabrianis <kabrianis@hellug.gr> for this
feature.
If start_html()'s -dtd parameter specifies an HTML 2.0, 3.2, 4.0 or
4.01 DTD, XHTML will automatically be disabled without needing to use
this pragma.
Special forms for importing HTML-tag functions
Many of the methods generate HTML tags. As described below, tag functions
automatically generate both the opening and closing tags. For example:
print h1('Level 1 Header');
produces
<h1>Level 1 Header</h1>
There will be some times when you want to produce the start and end tags
yourself. In this case, you can use the form start_tag_name and
end_tag_name, as in:
print start_h1,'Level 1 Header',end_h1;
Creating the HTML document header
print start_html(
-title => 'Secrets of the Pyramids',
-author => 'fred@capricorn.org',
-base => 'true',
-target => '_blank',
-meta => {'keywords'=>'pharaoh secret mummy',
'copyright' => 'copyright 1996 King Tut'},
-style => {'src'=>'/styles/style1.css'},
-BGCOLOR => 'blue'
);
The start_html() routine creates the top of the page, along with a lot of
optional information that controls the page's appearance and behavior.
This method returns a canned HTML header and the opening <body> tag. All
parameters are optional. In the named parameter form, recognized
parameters are -title, -author, -base, -xbase, -dtd, -lang and -target
(see below for the explanation). Any additional parameters you provide,
such as the unofficial BGCOLOR attribute, are added to the <body> tag.
Additional parameters must be proceeded by a hyphen.
The argument -xbase allows you to provide an HREF for the <base> tag
different from the current location, as in
-xbase => "http://home.mcom.com/"
All relative links will be interpreted relative to this tag.
The argument -target allows you to provide a default target frame for all
the links and fill-out forms on the page. This is a non-standard HTTP
feature which only works with some browsers!
-target => "answer_window"
All relative links will be interpreted relative to this tag. You add
arbitrary meta information to the header with the -meta argument. This
argument expects a reference to a hash containing name/value pairs of
meta information. These will be turned into a series of header <meta>
tags that look something like this:
<meta name="keywords" content="pharaoh secret mummy">
<meta name="description" content="copyright 1996 King Tut">
To create an HTTP-EQUIV type of <meta> tag, use -head, described below.
The -style argument is used to incorporate cascading stylesheets into
your code. See the section on CASCADING STYLESHEETS for more information.
The -lang argument is used to incorporate a language attribute into the
<html> tag. For example:
print $q->start_html( -lang => 'fr-CA' );
The default if not specified is "en-US" for US English, unless the -dtd
parameter specifies an HTML 2.0 or 3.2 DTD, in which case the lang
attribute is left off. You can force the lang attribute to left off in
other cases by passing an empty string (-lang=>'').
The -encoding argument can be used to specify the character set for
XHTML. It defaults to iso-8859-1 if not specified.
The -dtd argument can be used to specify a public DTD identifier string.
For example:
-dtd => '-//W3C//DTD HTML 4.01 Transitional//EN')
Alternatively, it can take public and system DTD identifiers as an array:
-dtd => [
'-//W3C//DTD HTML 4.01 Transitional//EN',
'http://www.w3.org/TR/html4/loose.dtd'
]
For the public DTD identifier to be considered, it must be valid.
Otherwise it will be replaced by the default DTD. If the public DTD
contains 'XHTML', CGI.pm will emit XML.
The -declare_xml argument, when used in conjunction with XHTML, will put
a <?xml> declaration at the top of the HTML header. The sole purpose of
this declaration is to declare the character set encoding. In the absence
of -declare_xml, the output HTML will contain a <meta> tag that specifies
the encoding, allowing the HTML to pass most validators. The default for
-declare_xml is false.
You can place other arbitrary HTML elements to the <head> section with
the -head tag. For example, to place a <link> element in the head
section, use this:
print start_html(
-head => Link({
-rel => 'shortcut icon',
-href => 'favicon.ico'
})
);
To incorporate multiple HTML elements into the <head> section, just pass
an array reference:
print start_html(
-head => [
Link({
-rel => 'next',
-href => 'http://www.capricorn.com/s2.html'
}),
Link({
-rel => 'previous',
-href => 'http://www.capricorn.com/s1.html'
})
]
);
And here's how to create an HTTP-EQUIV <meta> tag:
print start_html(
-head => meta({
-http_equiv => 'Content-Type',
-content => 'text/html'
})
);
JAVASCRIPTING: The -script, -noScript, -onLoad, -onMouseOver, -onMouseOut
and -onUnload parameters are used to add JavaScript calls to your pages.
-script should point to a block of text containing JavaScript function
definitions. This block will be placed within a <script> block inside the
HTML (not HTTP) header. The block is placed in the header in order to
give your page a fighting chance of having all its JavaScript functions
in place even if the user presses the stop button before the page has
loaded completely. CGI.pm attempts to format the script in such a way
that JavaScript-naive browsers will not choke on the code: unfortunately
there are some browsers that get confused by it nevertheless.
The -onLoad and -onUnload parameters point to fragments of JavaScript
code to execute when the page is respectively opened and closed by the
browser. Usually these parameters are calls to functions defined in the
-script field:
$q = CGI->new;
print header;
$JSCRIPT = <<END;
// Ask a silly question
function riddle_me_this() {
var r = prompt(
"What walks on four legs in the morning, " +
"two legs in the afternoon, " +
"and three legs in the evening?"
);
response(r);
}
// Get a silly answer
function response(answer) {
if (answer == "man")
alert("Right you are!");
else
alert("Wrong! Guess again.");
}
END
print start_html(
-title => 'The Riddle of the Sphinx',
-script => $JSCRIPT
);
Use the -noScript parameter to pass some HTML text that will be displayed
on browsers that do not have JavaScript (or browsers where JavaScript is
turned off).
The <script> tag, has several attributes including "type", "charset" and
"src". "src" allows you to keep JavaScript code in an external file. To
use these attributes pass a HASH reference in the -script parameter
containing one or more of -type, -src, or -code:
print $q->start_html(
-title => 'The Riddle of the Sphinx',
-script => {
-type => 'JAVASCRIPT',
-src => '/javascript/sphinx.js'}
);
print $q->(
-title => 'The Riddle of the Sphinx',
-script => {
-type => 'PERLSCRIPT',
-code => 'print "hello world!\n;"'
}
);
A final feature allows you to incorporate multiple <script> sections into
the header. Just pass the list of script sections as an array reference.
This allows you to specify different source files for different dialects
of JavaScript. Example:
print $q->start_html(
-title => 'The Riddle of the Sphinx',
-script => [
{
-type => 'text/javascript',
-src => '/javascript/utilities10.js'
},
{
-type => 'text/javascript',
-src => '/javascript/utilities11.js'
},
{
-type => 'text/jscript',
-src => '/javascript/utilities12.js'
},
{
-type => 'text/ecmascript',
-src => '/javascript/utilities219.js'
}
]
);
The option "-language" is a synonym for -type, and is supported for
backwards compatibility.
The old-style positional parameters are as follows:
Parameters:
1. The title
2. The author's e-mail address (will create a <link rev="MADE"> tag if
present
3. A 'true' flag if you want to include a <base> tag in the header. This
helps resolve relative addresses to absolute ones when the document
is moved, but makes the document hierarchy non-portable. Use with
care!
Other parameters you want to include in the <body> tag may be appended to
these. This is a good place to put HTML extensions, such as colors and
wallpaper patterns.
Ending the Html document:
print $q->end_html;
This ends an HTML document by printing the </body></html> tags.
CREATING STANDARD HTML ELEMENTS:
CGI.pm defines general HTML shortcut methods for many HTML tags. HTML
shortcuts are named after a single HTML element and return a fragment of
HTML text. Example:
print $q->blockquote(
"Many years ago on the island of",
$q->a({href=>"http://crete.org/"},"Crete"),
"there lived a Minotaur named",
$q->strong("Fred."),
),
$q->hr;
This results in the following HTML code (extra newlines have been added
for readability):
<blockquote>
Many years ago on the island of
<a href="http://crete.org/">Crete</a> there lived
a minotaur named <strong>Fred.</strong>
</blockquote>
<hr>
If you find the syntax for calling the HTML shortcuts awkward, you can
import them into your namespace and dispense with the object syntax
completely (see the next section for more details):
use CGI ':standard';
print blockquote(
"Many years ago on the island of",
a({href=>"http://crete.org/"},"Crete"),
"there lived a minotaur named",
strong("Fred."),
),
hr;
Providing arguments to HTML shortcuts
The HTML methods will accept zero, one or multiple arguments. If you
provide no arguments, you get a single tag:
print hr; # <hr>
If you provide one or more string arguments, they are concatenated
together with spaces and placed between opening and closing tags:
print h1("Chapter","1"); # <h1>Chapter 1</h1>"
If the first argument is a hash reference, then the keys and values of
the hash become the HTML tag's attributes:
print a({-href=>'fred.html',-target=>'_new'},
"Open a new frame");
<a href="fred.html",target="_new">Open a new frame</a>
You may dispense with the dashes in front of the attribute names if you
prefer:
print img {src=>'fred.gif',align=>'LEFT'};
<img align="LEFT" src="fred.gif">
Sometimes an HTML tag attribute has no argument. For example, ordered
lists can be marked as COMPACT. The syntax for this is an argument that
that points to an undef string:
print ol({compact=>undef},li('one'),li('two'),li('three'));
Prior to CGI.pm version 2.41, providing an empty ('') string as an
attribute argument was the same as providing undef. However, this has
changed in order to accommodate those who want to create tags of the form
<img alt="">. The difference is shown in these two pieces of code:
CODE RESULT
img({alt=>undef}) <img alt>
img({alt=>''}) <img alt="">
The distributive property of HTML shortcuts
One of the cool features of the HTML shortcuts is that they are
distributive. If you give them an argument consisting of a reference to
a list, the tag will be distributed across each element of the list. For
example, here's one way to make an ordered list:
print ul(
li({-type=>'disc'},['Sneezy','Doc','Sleepy','Happy'])
);
This example will result in HTML output that looks like this:
<ul>
<li type="disc">Sneezy</li>
<li type="disc">Doc</li>
<li type="disc">Sleepy</li>
<li type="disc">Happy</li>
</ul>
This is extremely useful for creating tables. For example:
print table({-border=>undef},
caption('When Should You Eat Your Vegetables?'),
Tr({-align=>'CENTER',-valign=>'TOP'},
[
th(['Vegetable', 'Breakfast','Lunch','Dinner']),
td(['Tomatoes' , 'no', 'yes', 'yes']),
td(['Broccoli' , 'no', 'no', 'yes']),
td(['Onions' , 'yes','yes', 'yes'])
]
)
);
HTML shortcuts and list interpolation
Consider this bit of code:
print blockquote(em('Hi'),'mom!'));
It will ordinarily return the string that you probably expect, namely:
<blockquote><em>Hi</em> mom!</blockquote>
Note the space between the element "Hi" and the element "mom!". CGI.pm
puts the extra space there using array interpolation, which is controlled
by the magic $" variable. Sometimes this extra space is not what you
want, for example, when you are trying to align a series of images. In
this case, you can simply change the value of $" to an empty string.
{
local($") = '';
print blockquote(em('Hi'),'mom!'));
}
I suggest you put the code in a block as shown here. Otherwise the
change to $" will affect all subsequent code until you explicitly reset
it.
Non-standard HTML shortcuts
A few HTML tags don't follow the standard pattern for various reasons.
comment() generates an HTML comment (<!-- comment -->). Call it like
print comment('here is my comment');
Since v5.00 any "--" in the text has a space inserted ("- -") so that the
text can't end the comment (or start a nested one) and inject markup.
Because of conflicts with built-in perl functions, the following
functions begin with initial caps:
Select
Tr
Link
Delete
Accept
Sub
In addition, start_html(), end_html(), start_form(), end_form(),
start_multipart_form() and all the fill-out form tags are special. See
their respective sections.
Autoescaping HTML
By default, all HTML that is emitted by the form-generating functions is
passed through a function called escapeHTML():
$escaped_string = escapeHTML("unescaped string");
Escape HTML formatting characters in a string. Internally this calls
HTML::Entities (encode_entities) so really you should just use that
instead - the default list of chars that will be encoded (passed to
the HTML::Entities encode_entities method) is:
& < > " \x8b \x9b '
you can control this list by setting the value of
$CGI::ENCODE_ENTITIES:
# only encode < >
$CGI::ENCODE_ENTITIES = q{<>}
if you want to encode all entities then undef $CGI::ENCODE_ENTITIES:
# encode all entities
$CGI::ENCODE_ENTITIES = undef;
The automatic escaping does not apply to other shortcuts, such as h1().
You should call escapeHTML() yourself on untrusted data in order to
protect your pages against nasty tricks that people may enter into
guestbooks, etc.. To change the character set, use charset(). To turn
autoescaping off completely, use autoEscape(0):
$charset = charset([$charset]);
Get or set the current character set.
$flag = autoEscape([$flag]);
Get or set the value of the autoescape flag.
CREATING FILL-OUT FORMS:
General note The various form-creating methods all return strings to the
caller, containing the tag or tags that will create the requested form
element. You are responsible for actually printing out these strings.
It's set up this way so that you can place formatting tags around the
form elements.
Another note The default values that you specify for the forms are only
used the first time the script is invoked (when there is no query
string). On subsequent invocations of the script (when there is a query
string), the former values are used even if they are blank.
If you want to change the value of a field from its previous value, you
have two choices:
(1) call the param() method to set it.
(2) use the -override (alias -force) parameter (a new feature in version
2.15). This forces the default value to be used, regardless of the
previous value:
print textfield(-name=>'field_name',
-default=>'starting value',
-override=>1,
-size=>50,
-maxlength=>80);
Yet another note By default, the text and labels of form elements are
escaped according to HTML rules. This means that you can safely use
"<CLICK ME>" as the label for a button. However, it also interferes with
your ability to incorporate special HTML character sequences, such as
Á, into your fields. If you wish to turn off automatic escaping,
call the autoEscape() method with a false value immediately after
creating the CGI object:
$q = CGI->new;
$q->autoEscape(0);
Note that autoEscape() is exclusively used to effect the behavior of how
some CGI.pm HTML generation functions handle escaping. Calling
escapeHTML() explicitly will always escape the HTML.
A Lurking Trap! Some of the form-element generating methods return
multiple tags. In a scalar context, the tags will be concatenated
together with spaces, or whatever is the current value of the $" global.
In a list context, the methods will return a list of elements, allowing
you to modify them if you wish. Usually you will not notice this
behavior, but beware of this:
printf("%s\n",end_form())
end_form() produces several tags, and only the first of them will be
printed because the format only expects one value.
<p>
Creating an isindex tag
print isindex(-action=>$action);
-or-
print isindex($action);
Prints out an <isindex> tag. Not very exciting. The parameter -action
specifies the URL of the script to process the query. The default is to
process the query with the current script.
Starting and ending a form
print start_form(-method=>$method,
-action=>$action,
-enctype=>$encoding);
<... various form stuff ...>
print end_form;
-or-
print start_form($method,$action,$encoding);
<... various form stuff ...>
print end_form;
start_form() will return a <form> tag with the optional method, action
and form encoding that you specify. The defaults are:
method: POST
action: this script
enctype: application/x-www-form-urlencoded for non-XHTML
multipart/form-data for XHTML, see multipart/form-data below.
end_form() returns the closing </form> tag.
start_form()'s enctype argument tells the browser how to package the
various fields of the form before sending the form to the server. Two
values are possible:
application/x-www-form-urlencoded
This is the older type of encoding. It is compatible with many CGI
scripts and is suitable for short fields containing text data. For
your convenience, CGI.pm stores the name of this encoding type in
&CGI::URL_ENCODED.
multipart/form-data
This is the newer type of encoding. It is suitable for forms that
contain very large fields or that are intended for transferring
binary data. Most importantly, it enables the "file upload" feature.
For your convenience, CGI.pm stores the name of this encoding type in
&CGI::MULTIPART
Forms that use this type of encoding are not easily interpreted by
CGI scripts unless they use CGI.pm or another library designed to
handle them.
If XHTML is activated (the default), then forms will be automatically
created using this type of encoding.
The start_form() method uses the older form of encoding by default unless
XHTML is requested. If you want to use the newer form of encoding by
default, you can call start_multipart_form() instead of start_form().
The method end_multipart_form() is an alias to end_form().
JAVASCRIPTING: The -name and -onSubmit parameters are provided for use
with JavaScript. The -name parameter gives the form a name so that it
can be identified and manipulated by JavaScript functions. -onSubmit
should point to a JavaScript function that will be executed just before
the form is submitted to your server. You can use this opportunity to
check the contents of the form for consistency and completeness. If you
find something wrong, you can put up an alert box or maybe fix things up
yourself. You can abort the submission by returning false from this
function.
Usually the bulk of JavaScript functions are defined in a <script> block
in the HTML header and -onSubmit points to one of these function call.
See start_html() for details.
Form elements
After starting a form, you will typically create one or more textfields,
popup menus, radio groups and other form elements. Each of these
elements takes a standard set of named arguments. Some elements also
have optional arguments. The standard arguments are as follows:
-name
The name of the field. After submission this name can be used to
retrieve the field's value using the param() method.
-value, -values
The initial value of the field which will be returned to the script
after form submission. Some form elements, such as text fields, take
a single scalar -value argument. Others, such as popup menus, take a
reference to an array of values. The two arguments are synonyms.
-tabindex
A numeric value that sets the order in which the form element
receives focus when the user presses the tab key. Elements with lower
values receive focus first.
-id A string identifier that can be used to identify this element to
JavaScript and DHTML.
-override
A boolean, which, if true, forces the element to take on the value
specified by -value, overriding the sticky behavior described earlier
for the -nosticky pragma.
-onChange, -onFocus, -onBlur, -onMouseOver, -onMouseOut, -onSelect
These are used to assign JavaScript event handlers. See the
JavaScripting section for more details.
Other common arguments are described in the next section. In addition to
these, all attributes described in the HTML specifications are supported.
Creating a text field
print textfield(-name=>'field_name',
-value=>'starting value',
-size=>50,
-maxlength=>80);
-or-
print textfield('field_name','starting value',50,80);
textfield() will return a text input field.
Parameters
1. The first parameter is the required name for the field (-name).
2. The optional second parameter is the default starting value for the
field contents (-value, formerly known as -default).
3. The optional third parameter is the size of the field in
characters (-size).
4. The optional fourth parameter is the maximum number of characters the
field will accept (-maxlength).
As with all these methods, the field will be initialized with its
previous contents from earlier invocations of the script. When the form
is processed, the value of the text field can be retrieved with:
$value = param('foo');
If you want to reset it from its initial value after the script has been
called once, you can do so like this:
param('foo',"I'm taking over this value!");
Creating a big text field
print textarea(-name=>'foo',
-default=>'starting value',
-rows=>10,
-columns=>50);
-or
print textarea('foo','starting value',10,50);
textarea() is just like textfield, but it allows you to specify rows and
columns for a multiline text entry box. You can provide a starting value
for the field, which can be long and contain multiple lines.
Creating a password field
print password_field(-name=>'secret',
-value=>'starting value',
-size=>50,
-maxlength=>80);
-or-
print password_field('secret','starting value',50,80);
password_field() is identical to textfield(), except that its contents
will be starred out on the web page.
Creating a file upload field
print filefield(-name=>'uploaded_file',
-default=>'starting value',
-size=>50,
-maxlength=>80);
-or-
print filefield('uploaded_file','starting value',50,80);
filefield() will return a file upload field. In order to take full
advantage of this you must use the new multipart encoding scheme for the
form. You can do this either by calling start_form() with an encoding
type of &CGI::MULTIPART, or by calling the new method
start_multipart_form() instead of vanilla start_form().
Parameters
1. The first parameter is the required name for the field (-name).
2. The optional second parameter is the starting value for the field
contents to be used as the default file name (-default).
For security reasons, browsers don't pay any attention to this field,
and so the starting value will always be blank. Worse, the field
loses its "sticky" behavior and forgets its previous contents. The
starting value field is called for in the HTML specification,
however, and possibly some browser will eventually provide support
for it.
3. The optional third parameter is the size of the field in characters
(-size).
4. The optional fourth parameter is the maximum number of characters the
field will accept (-maxlength).
JAVASCRIPTING: The -onChange, -onFocus, -onBlur, -onMouseOver,
-onMouseOut and -onSelect parameters are recognized. See textfield() for
details.
Creating a popup menu
print popup_menu('menu_name',
['eenie','meenie','minie'],
'meenie');
-or-
%labels = ('eenie'=>'your first choice',
'meenie'=>'your second choice',
'minie'=>'your third choice');
%attributes = ('eenie'=>{'class'=>'class of first choice'});
print popup_menu('menu_name',
['eenie','meenie','minie'],
'meenie',\%labels,\%attributes);
-or (named parameter style)-
print popup_menu(-name=>'menu_name',
-values=>['eenie','meenie','minie'],
-default=>['meenie','minie'],
-labels=>\%labels,
-attributes=>\%attributes);
popup_menu() creates a menu. Please note that the -multiple option will
be ignored if passed - use scrolling_list() if you want to create a menu
that supports multiple selections
1. The required first argument is the menu's name (-name).
2. The required second argument (-values) is an array reference
containing the list of menu items in the menu. You can pass the
method an anonymous array, as shown in the example, or a reference to
a named array, such as "\@foo".
3. The optional third parameter (-default) is the name of the default
menu choice. If not specified, the first item will be the default.
The values of the previous choice will be maintained across queries.
Pass an array reference to select multiple defaults.
4. The optional fourth parameter (-labels) is provided for people who
want to use different values for the user-visible label inside the
popup menu and the value returned to your script. It's a pointer to
an hash relating menu values to user-visible labels. If you leave
this parameter blank, the menu values will be displayed by default.
(You can also leave a label undefined if you want to).
5. The optional fifth parameter (-attributes) is provided to assign any
of the common HTML attributes to an individual menu item. It's a
pointer to a hash relating menu values to another hash with the
attribute's name as the key and the attribute's value as the value.
When the form is processed, the selected value of the popup menu can be
retrieved using:
$popup_menu_value = param('menu_name');
Creating an option group
Named parameter style
print popup_menu(-name=>'menu_name',
-values=>[qw/eenie meenie minie/,
optgroup(-name=>'optgroup_name',
-values => ['moe','catch'],
-attributes=>{'catch'=>{'class'=>'red'}})],
-labels=>{'eenie'=>'one',
'meenie'=>'two',
'minie'=>'three'},
-default=>'meenie');
Old style
print popup_menu('menu_name',
['eenie','meenie','minie',
optgroup('optgroup_name', ['moe', 'catch'],
{'catch'=>{'class'=>'red'}})],'meenie',
{'eenie'=>'one','meenie'=>'two','minie'=>'three'});
optgroup() creates an option group within a popup menu.
1. The required first argument (-name) is the label attribute of the
optgroup and is not inserted in the parameter list of the query.
2. The required second argument (-values) is an array reference
containing the list of menu items in the menu. You can pass the
method an anonymous array, as shown in the example, or a reference to
a named array, such as \@foo. If you pass a HASH reference, the keys
will be used for the menu values, and the values will be used for the
menu labels (see -labels below).
3. The optional third parameter (-labels) allows you to pass a reference
to a hash containing user-visible labels for one or more of the menu
items. You can use this when you want the user to see one menu
string, but have the browser return your program a different one. If
you don't specify this, the value string will be used instead
("eenie", "meenie" and "minie" in this example). This is equivalent
to using a hash reference for the -values parameter.
4. An optional fourth parameter (-labeled) can be set to a true value
and indicates that the values should be used as the label attribute
for each option element within the optgroup.
5. An optional fifth parameter (-novals) can be set to a true value and
indicates to suppress the val attribute in each option element within
the optgroup.
See the discussion on optgroup at W3C
(http://www.w3.org/TR/REC-html40/interact/forms.html#edef-OPTGROUP)
for details.
6. An optional sixth parameter (-attributes) is provided to assign any
of the common HTML attributes to an individual menu item. It's a
pointer to a hash relating menu values to another hash with the
attribute's name as the key and the attribute's value as the value.
Creating a scrolling list
print scrolling_list('list_name',
['eenie','meenie','minie','moe'],
['eenie','moe'],5,'true',{'moe'=>{'class'=>'red'}});
-or-
print scrolling_list('list_name',
['eenie','meenie','minie','moe'],
['eenie','moe'],5,'true',
\%labels,%attributes);
-or-
print scrolling_list(-name=>'list_name',
-values=>['eenie','meenie','minie','moe'],
-default=>['eenie','moe'],
-size=>5,
-multiple=>'true',
-labels=>\%labels,
-attributes=>\%attributes);
scrolling_list() creates a scrolling list.
Parameters:
1. The first and second arguments are the list name (-name) and values
(-values). As in the popup menu, the second argument should be an
array reference.
2. The optional third argument (-default) can be either a reference to a
list containing the values to be selected by default, or can be a
single value to select. If this argument is missing or undefined,
then nothing is selected when the list first appears. In the named
parameter version, you can use the synonym "-defaults" for this
parameter.
3. The optional fourth argument is the size of the list (-size).
4. The optional fifth argument can be set to true to allow multiple
simultaneous selections (-multiple). Otherwise only one selection
will be allowed at a time.
5. The optional sixth argument is a pointer to a hash containing long
user-visible labels for the list items (-labels). If not provided,
the values will be displayed.
6. The optional sixth parameter (-attributes) is provided to assign any
of the common HTML attributes to an individual menu item. It's a
pointer to a hash relating menu values to another hash with the
attribute's name as the key and the attribute's value as the value.
When this form is processed, all selected list items will be returned
as a list under the parameter name 'list_name'. The values of the
selected items can be retrieved with:
@selected = param('list_name');
Creating a group of related checkboxes
print checkbox_group(-name=>'group_name',
-values=>['eenie','meenie','minie','moe'],
-default=>['eenie','moe'],
-linebreak=>'true',
-disabled => ['moe'],
-labels=>\%labels,
-attributes=>\%attributes);
print checkbox_group('group_name',
['eenie','meenie','minie','moe'],
['eenie','moe'],'true',\%labels,
{'moe'=>{'class'=>'red'}});
HTML3-COMPATIBLE BROWSERS ONLY:
print checkbox_group(-name=>'group_name',
-values=>['eenie','meenie','minie','moe'],
-rows=2,-columns=>2);
checkbox_group() creates a list of checkboxes that are related by the
same name.
Parameters:
1. The first and second arguments are the checkbox name and values,
respectively (-name and -values). As in the popup menu, the second
argument should be an array reference. These values are used for the
user-readable labels printed next to the checkboxes as well as for
the values passed to your script in the query string.
2. The optional third argument (-default) can be either a reference to a
list containing the values to be checked by default, or can be a
single value to checked. If this argument is missing or undefined,
then nothing is selected when the list first appears.
3. The optional fourth argument (-linebreak) can be set to true to place
line breaks between the checkboxes so that they appear as a vertical
list. Otherwise, they will be strung together on a horizontal line.
The optional -labels argument is a pointer to a hash relating the
checkbox values to the user-visible labels that will be printed next to
them. If not provided, the values will be used as the default.
The optional parameters -rows, and -columns cause checkbox_group() to
return an HTML3 compatible table containing the checkbox group formatted
with the specified number of rows and columns. You can provide just the
-columns parameter if you wish; checkbox_group will calculate the correct
number of rows for you.
The option -disabled takes an array of checkbox values and disables them
by greying them out (this may not be supported by all browsers).
The optional -attributes argument is provided to assign any of the common
HTML attributes to an individual menu item. It's a pointer to a hash
relating menu values to another hash with the attribute's name as the key
and the attribute's value as the value.
The optional -tabindex argument can be used to control the order in which
radio buttons receive focus when the user presses the tab button. If
passed a scalar numeric value, the first element in the group will
receive this tab index and subsequent elements will be incremented by
one. If given a reference to an array of radio button values, then the
indexes will be jiggered so that the order specified in the array will
correspond to the tab order. You can also pass a reference to a hash in
which the hash keys are the radio button values and the values are the
tab indexes of each button. Examples:
-tabindex => 100 # this group starts at index 100 and counts up
-tabindex => ['moe','minie','eenie','meenie'] # tab in this order
-tabindex => {meenie=>100,moe=>101,minie=>102,eenie=>200} # tab in this order
The optional -labelattributes argument will contain attributes attached
to the <label> element that surrounds each button.
When the form is processed, all checked boxes will be returned as a list
under the parameter name 'group_name'. The values of the "on" checkboxes
can be retrieved with:
@turned_on = param('group_name');
The value returned by checkbox_group() is actually an array of button
elements. You can capture them and use them within tables, lists, or in
other creative ways:
@h = checkbox_group(-name=>'group_name',-values=>\@values);
&use_in_creative_way(@h);
Creating a standalone checkbox
print checkbox(-name=>'checkbox_name',
-checked=>1,
-value=>'ON',
-label=>'CLICK ME');
-or-
print checkbox('checkbox_name','checked','ON','CLICK ME');
checkbox() is used to create an isolated checkbox that isn't logically
related to any others.
Parameters:
1. The first parameter is the required name for the checkbox (-name).
It will also be used for the user-readable label printed next to the
checkbox.
2. The optional second parameter (-checked) specifies that the checkbox
is turned on by default. Synonyms are -selected and -on.
3. The optional third parameter (-value) specifies the value of the
checkbox when it is checked. If not provided, the word "on" is
assumed.
4. The optional fourth parameter (-label) is the user-readable label to
be attached to the checkbox. If not provided, the checkbox name is
used.
The value of the checkbox can be retrieved using:
$turned_on = param('checkbox_name');
Creating a radio button group
print radio_group(-name=>'group_name',
-values=>['eenie','meenie','minie'],
-default=>'meenie',
-linebreak=>'true',
-labels=>\%labels,
-attributes=>\%attributes);
-or-
print radio_group('group_name',['eenie','meenie','minie'],
'meenie','true',\%labels,\%attributes);
HTML3-COMPATIBLE BROWSERS ONLY:
print radio_group(-name=>'group_name',
-values=>['eenie','meenie','minie','moe'],
-rows=2,-columns=>2);
radio_group() creates a set of logically-related radio buttons (turning
one member of the group on turns the others off)
Parameters:
1. The first argument is the name of the group and is required (-name).
2. The second argument (-values) is the list of values for the radio
buttons. The values and the labels that appear on the page are
identical. Pass an array reference in the second argument, either
using an anonymous array, as shown, or by referencing a named array
as in "\@foo".
3. The optional third parameter (-default) is the name of the default
button to turn on. If not specified, the first item will be the
default. You can provide a nonexistent button name, such as "-" to
start up with no buttons selected.
4. The optional fourth parameter (-linebreak) can be set to 'true' to
put line breaks between the buttons, creating a vertical list.
5. The optional fifth parameter (-labels) is a pointer to an associative
array relating the radio button values to user-visible labels to be
used in the display. If not provided, the values themselves are
displayed.
All modern browsers can take advantage of the optional parameters -rows,
and -columns. These parameters cause radio_group() to return an HTML3
compatible table containing the radio group formatted with the specified
number of rows and columns. You can provide just the -columns parameter
if you wish; radio_group will calculate the correct number of rows for
you.
To include row and column headings in the returned table, you can use the
-rowheaders and -colheaders parameters. Both of these accept a pointer
to an array of headings to use. The headings are just decorative. They
don't reorganize the interpretation of the radio buttons -- they're still
a single named unit.
The optional -tabindex argument can be used to control the order in which
radio buttons receive focus when the user presses the tab button. If
passed a scalar numeric value, the first element in the group will
receive this tab index and subsequent elements will be incremented by
one. If given a reference to an array of radio button values, then the
indexes will be jiggered so that the order specified in the array will
correspond to the tab order. You can also pass a reference to a hash in
which the hash keys are the radio button values and the values are the
tab indexes of each button. Examples:
-tabindex => 100 # this group starts at index 100 and counts up
-tabindex => ['moe','minie','eenie','meenie'] # tab in this order
-tabindex => {meenie=>100,moe=>101,minie=>102,eenie=>200} # tab in this order
The optional -attributes argument is provided to assign any of the common
HTML attributes to an individual menu item. It's a pointer to a hash
relating menu values to another hash with the attribute's name as the key
and the attribute's value as the value.
The optional -labelattributes argument will contain attributes attached
to the <label> element that surrounds each button.
When the form is processed, the selected radio button can be retrieved
using:
$which_radio_button = param('group_name');
The value returned by radio_group() is actually an array of button
elements. You can capture them and use them within tables, lists, or in
other creative ways:
@h = radio_group(-name=>'group_name',-values=>\@values);
&use_in_creative_way(@h);
Creating a submit button
print submit(-name=>'button_name',
-value=>'value');
-or-
print submit('button_name','value');
submit() will create the query submission button. Every form should have
one of these.
Parameters:
1. The first argument (-name) is optional. You can give the button a
name if you have several submission buttons in your form and you want
to distinguish between them.
2. The second argument (-value) is also optional. This gives the button
a value that will be passed to your script in the query string. The
name will also be used as the user-visible label.
3. You can use -label as an alias for -value. I always get confused
about which of -name and -value changes the user-visible label on the
button.
You can figure out which button was pressed by using different values for
each one:
$which_one = param('button_name');
Creating a reset button
print reset
reset() creates the "reset" button. Note that it restores the form to
its value from the last time the script was called, NOT necessarily to
the defaults.
Note that this conflicts with the perl reset() built-in. Use
CORE::reset() to get the original reset function.
Creating a default button
print defaults('button_label')
defaults() creates a button that, when invoked, will cause the form to be
completely reset to its defaults, wiping out all the changes the user
ever made.
Creating a hidden field
print hidden(-name=>'hidden_name',
-default=>['value1','value2'...]);
-or-
print hidden('hidden_name','value1','value2'...);
hidden() produces a text field that can't be seen by the user. It is
useful for passing state variable information from one invocation of the
script to the next.
Parameters:
1. The first argument is required and specifies the name of this field
(-name).
2. The second argument is also required and specifies its value
(-default). In the named parameter style of calling, you can provide
a single value here or a reference to a whole list
Fetch the value of a hidden field this way:
$hidden_value = param('hidden_name');
Note, that just like all the other form elements, the value of a hidden
field is "sticky". If you want to replace a hidden field with some other
values after the script has been called once you'll have to do it
manually:
param('hidden_name','new','values','here');
Creating a clickable image button
print image_button(-name=>'button_name',
-src=>'/source/URL',
-align=>'MIDDLE');
-or-
print image_button('button_name','/source/URL','MIDDLE');
image_button() produces a clickable image. When it's clicked on the
position of the click is returned to your script as "button_name.x" and
"button_name.y", where "button_name" is the name you've assigned to it.
Parameters:
1. The first argument (-name) is required and specifies the name of this
field.
2. The second argument (-src) is also required and specifies the URL
3. The third option (-align, optional) is an alignment type, and may be
TOP, BOTTOM or MIDDLE
Fetch the value of the button this way:
$x = param('button_name.x');
$y = param('button_name.y');
Creating a javascript action button
print button(-name=>'button_name',
-value=>'user visible label',
-onClick=>"do_something()");
-or-
print button('button_name',"user visible value","do_something()");
button() produces an "<input>" tag with "type="button"". When it's
pressed the fragment of JavaScript code pointed to by the -onClick
parameter will be executed.
WORKING WITH FRAMES
It's possible for CGI.pm scripts to write into several browser panels and
windows using the HTML 4 frame mechanism. There are three techniques for
defining new frames programmatically:
1. Create a <Frameset> document
After writing out the HTTP header, instead of creating a standard
HTML document using the start_html() call, create a <frameset>
document that defines the frames on the page. Specify your script(s)
(with appropriate parameters) as the SRC for each of the frames.
There is no specific support for creating <frameset> sections in
CGI.pm, but the HTML is very simple to write.
2. Specify the destination for the document in the HTTP header
You may provide a -target parameter to the header() method:
print header(-target=>'ResultsWindow');
This will tell the browser to load the output of your script into the
frame named "ResultsWindow". If a frame of that name doesn't already
exist, the browser will pop up a new window and load your script's
document into that. There are a number of magic names that you can
use for targets. See the HTML "<frame>" documentation for details.
3. Specify the destination for the document in the <form> tag
You can specify the frame to load in the FORM tag itself. With
CGI.pm it looks like this:
print start_form(-target=>'ResultsWindow');
When your script is reinvoked by the form, its output will be loaded
into the frame named "ResultsWindow". If one doesn't already exist a
new window will be created.
The script "frameset.cgi" in the examples directory shows one way to
create pages in which the fill-out form and the response live in side-by-
side frames.
SUPPORT FOR JAVASCRIPT
The usual way to use JavaScript is to define a set of functions in a
<SCRIPT> block inside the HTML header and then to register event handlers
in the various elements of the page. Events include such things as the
mouse passing over a form element, a button being clicked, the contents
of a text field changing, or a form being submitted. When an event occurs
that involves an element that has registered an event handler, its
associated JavaScript code gets called.
The elements that can register event handlers include the <BODY> of an
HTML document, hypertext links, all the various elements of a fill-out
form, and the form itself. There are a large number of events, and each
applies only to the elements for which it is relevant. Here is a partial
list:
onLoad
The browser is loading the current document. Valid in:
+ The HTML <BODY> section only.
onUnload
The browser is closing the current page or frame. Valid for:
+ The HTML <BODY> section only.
onSubmit
The user has pressed the submit button of a form. This event happens
just before the form is submitted, and your function can return a
value of false in order to abort the submission. Valid for:
+ Forms only.
onClick
The mouse has clicked on an item in a fill-out form. Valid for:
+ Buttons (including submit, reset, and image buttons)
+ Checkboxes
+ Radio buttons
onChange
The user has changed the contents of a field. Valid for:
+ Text fields
+ Text areas
+ Password fields
+ File fields
+ Popup Menus
+ Scrolling lists
onFocus
The user has selected a field to work with. Valid for:
+ Text fields
+ Text areas
+ Password fields
+ File fields
+ Popup Menus
+ Scrolling lists
onBlur
The user has deselected a field (gone to work somewhere else). Valid
for:
+ Text fields
+ Text areas
+ Password fields
+ File fields
+ Popup Menus
+ Scrolling lists
onSelect
The user has changed the part of a text field that is selected.
Valid for:
+ Text fields
+ Text areas
+ Password fields
+ File fields
onMouseOver
The mouse has moved over an element.
+ Text fields
+ Text areas
+ Password fields
+ File fields
+ Popup Menus
+ Scrolling lists
onMouseOut
The mouse has moved off an element.
+ Text fields
+ Text areas
+ Password fields
+ File fields
+ Popup Menus
+ Scrolling lists
In order to register a JavaScript event handler with an HTML element,
just use the event name as a parameter when you call the corresponding
CGI method. For example, to have your validateAge() JavaScript code
executed every time the textfield named "age" changes, generate the field
like this:
print textfield(-name=>'age',-onChange=>"validateAge(this)");
This example assumes that you've already declared the validateAge()
function by incorporating it into a <SCRIPT> block. The CGI.pm
start_html() method provides a convenient way to create this section.
Similarly, you can create a form that checks itself over for consistency
and alerts the user if some essential value is missing by creating it
this way:
print start_form(-onSubmit=>"validateMe(this)");
See the javascript.cgi script for a demonstration of how this all works.
LIMITED SUPPORT FOR CASCADING STYLE SHEETS
CGI.pm has limited support for HTML3's cascading style sheets (css). To
incorporate a stylesheet into your document, pass the start_html() method
a -style parameter. The value of this parameter may be a scalar, in
which case it is treated as the source URL for the stylesheet, or it may
be a hash reference. In the latter case you should provide the hash with
one or more of -src or -code. -src points to a URL where an externally-
defined stylesheet can be found. -code points to a scalar value to be
incorporated into a <style> section. Style definitions in -code override
similarly-named ones in -src, hence the name "cascading."
You may also specify the type of the stylesheet by adding the optional
-type parameter to the hash pointed to by -style. If not specified, the
style defaults to 'text/css'.
To refer to a style within the body of your document, add the -class
parameter to any HTML element:
print h1({-class=>'Fancy'},'Welcome to the Party');
Or define styles on the fly with the -style parameter:
print h1({-style=>'Color: red;'},'Welcome to Hell');
You may also use the new span() element to apply a style to a section of
text:
print span({-style=>'Color: red;'},
h1('Welcome to Hell'),
"Where did that handbasket get to?"
);
Note that you must import the ":html3" definitions to have the span()
method available. Here's a quick and dirty example of using CSS's. See
the CSS specification at http://www.w3.org/Style/CSS/ for more
information.
use CGI qw/:standard :html3/;
#here's a stylesheet incorporated directly into the page
$newStyle=<<END;
<!--
P.Tip {
margin-right: 50pt;
margin-left: 50pt;
color: red;
}
P.Alert {
font-size: 30pt;
font-family: sans-serif;
color: red;
}
-->
END
print header();
print start_html( -title=>'CGI with Style',
-style=>{-src=>'http://www.capricorn.com/style/st1.css',
-code=>$newStyle}
);
print h1('CGI with Style'),
p({-class=>'Tip'},
"Better read the cascading style sheet spec before playing with this!"),
span({-style=>'color: magenta'},
"Look Mom, no hands!",
p(),
"Whooo wee!"
);
print end_html;
Pass an array reference to -code or -src in order to incorporate multiple
stylesheets into your document.
Should you wish to incorporate a verbatim stylesheet that includes
arbitrary formatting in the header, you may pass a -verbatim tag to the
-style hash, as follows:
print start_html (-style => {-verbatim => '@import
url("/server-common/css/'.$cssFile.'");',
-src => '/server-common/css/core.css'});
This will generate an HTML header that contains this:
<link rel="stylesheet" type="text/css" href="/server-common/css/core.css">
<style type="text/css">
@import url("/server-common/css/main.css");
</style>
Any additional arguments passed in the -style value will be incorporated
into the <link> tag. For example:
start_html(-style=>{-src=>['/styles/print.css','/styles/layout.css'],
-media => 'all'});
This will give:
<link rel="stylesheet" type="text/css" href="/styles/print.css" media="all"/>
<link rel="stylesheet" type="text/css" href="/styles/layout.css" media="all"/>
<p>
To make more complicated <link> tags, use the Link() function and pass it
to start_html() in the -head argument, as in:
@h = (Link({-rel=>'stylesheet',-type=>'text/css',-src=>'/ss/ss.css',-media=>'all'}),
Link({-rel=>'stylesheet',-type=>'text/css',-src=>'/ss/fred.css',-media=>'paper'}));
print start_html({-head=>\@h})
To create primary and "alternate" stylesheet, use the -alternate option:
start_html(-style=>{-src=>[
{-src=>'/styles/print.css'},
{-src=>'/styles/alt.css',-alternate=>1}
]
});
Dumping out all the name/value pairs
The Dump() method produces a string consisting of all the query's
name/value pairs formatted nicely as a nested list. This is useful for
debugging purposes:
print Dump
Produces something that looks like:
<ul>
<li>name1
<ul>
<li>value1
<li>value2
</ul>
<li>name2
<ul>
<li>value1
</ul>
</ul>
As a shortcut, you can interpolate the entire CGI object into a string
and it will be replaced with the a nice HTML dump shown above:
$q=CGI->new;
print "<h2>Current Values</h2> $q\n";
BUGS
Address bug reports and comments to:
<https://github.com/leejo/CGI.pm/issues>
See the <https://github.com/leejo/CGI.pm/blob/master/CONTRIBUTING.md>
file for information on raising issues and contributing
The original bug tracker can be found at:
<https://rt.cpan.org/Public/Dist/Display.html?Queue=CGI.pm>
SEE ALSO
CGI(3) - The original source of this documentation / functionality
perl v5.34.3 2026-11-09 CGI::HTML::Functions(3)
cgi 5.20.0 - Generated Tue Nov 10 07:46:19 CST 2026