HTML::Form(3) User Contributed Perl Documentation HTML::Form(3)
NAME
HTML::Form - Class that represents an HTML form element
VERSION
version 6.07
SYNOPSIS
use HTML::Form;
$form = HTML::Form->parse($html, $base_uri);
$form->value(query => "Perl");
use LWP::UserAgent;
$ua = LWP::UserAgent->new;
$response = $ua->request($form->click);
DESCRIPTION
Objects of the "HTML::Form" class represents a single HTML "<form> ...
</form>" instance. A form consists of a sequence of inputs that
usually have names, and which can take on various values. The state of
a form can be tweaked and it can then be asked to provide HTTP::Request
objects that can be passed to the request() method of LWP::UserAgent.
The following methods are available:
@forms = HTML::Form->parse( $html_document, $base_uri )
@forms = HTML::Form->parse( $html_document, base => $base_uri, %opt )
@forms = HTML::Form->parse( $response, %opt )
The parse() class method will parse an HTML document and build up
"HTML::Form" objects for each <form> element found. If called in
scalar context only returns the first <form>. Returns an empty
list if there are no forms to be found.
The required arguments is the HTML document to parse
($html_document) and the URI used to retrieve the document
($base_uri). The base URI is needed to resolve relative action
URIs. The provided HTML document should be a Unicode string (or
US-ASCII).
By default HTML::Form assumes that the original document was UTF-8
encoded and thus encode forms that don't specify an explicit
accept-charset as UTF-8. The charset assumed can be overridden by
providing the "charset" option to parse(). It's a good idea to be
explicit about this parameter as well, thus the recommended
simplest invocation becomes:
my @forms = HTML::Form->parse(
Encode::decode($encoding, $html_document_bytes),
base => $base_uri,
charset => $encoding,
);
If the document was retrieved with LWP then the response object
provide methods to obtain a proper value for "base" and "charset":
my $ua = LWP::UserAgent->new;
my $response = $ua->get("http://www.example.com/form.html");
my @forms = HTML::Form->parse($response->decoded_content,
base => $response->base,
charset => $response->content_charset,
);
In fact, the parse() method can parse from an HTTP::Response object
directly, so the example above can be more conveniently written as:
my $ua = LWP::UserAgent->new;
my $response = $ua->get("http://www.example.com/form.html");
my @forms = HTML::Form->parse($response);
Note that any object that implements a decoded_content(), base()
and content_charset() method with similar behaviour as
HTTP::Response will do.
Additional options might be passed in to control how the parse
method behaves. The following are all the options currently
recognized:
"base => $uri"
This is the URI used to retrieve the original document. This
option is not optional ;-)
"charset => $str"
Specify what charset the original document was encoded in.
This is used as the default for accept_charset. If not
provided this defaults to "UTF-8".
"verbose => $bool"
Warn (print messages to STDERR) about any bad HTML form
constructs found. You can trap these with $SIG{__WARN__}. The
default is not to issue warnings.
"strict => $bool"
Initialize any form objects with the given strict attribute.
If the strict is turned on the methods that change values of
the form will croak if you try to set illegal values or modify
readonly fields. The default is not to be strict.
$form->push_input( $type, \%attr, $verbose )
This method adds additional inputs to the form. The first argument
is the type of input (e.g. hidden, option, etc.). The second
argument is a reference to a hash of the input attributes. The
third argument is optional, and will issue warnings about unknown
input types.
Example:
push_input( 'hidden', {
name => 'NewFormElement',
id => 'NewFormElementId',
value => 'some value',
});
$method = $form->method
$form->method( $new_method )
This method is gets/sets the method name used for the HTTP::Request
generated. It is a string like "GET" or "POST".
$action = $form->action
$form->action( $new_action )
This method gets/sets the URI which we want to apply the request
method to.
$enctype = $form->enctype
$form->enctype( $new_enctype )
This method gets/sets the encoding type for the form data. It is a
string like "application/x-www-form-urlencoded" or
"multipart/form-data".
$accept = $form->accept_charset
$form->accept_charset( $new_accept )
This method gets/sets the list of charset encodings that the server
processing the form accepts. Current implementation supports only
one-element lists. Default value is "UNKNOWN" which we interpret
as a request to use document charset as specified by the 'charset'
parameter of the parse() method.
$value = $form->attr( $name )
$form->attr( $name, $new_value )
This method give access to the original HTML attributes of the
<form> tag. The $name should always be passed in lower case.
Example:
@f = HTML::Form->parse( $html, $foo );
@f = grep $_->attr("id") eq "foo", @f;
die "No form named 'foo' found" unless @f;
$foo = shift @f;
$bool = $form->strict
$form->strict( $bool )
Gets/sets the strict attribute of a form. If the strict is turned
on the methods that change values of the form will croak if you try
to set illegal values or modify readonly fields. The default is
not to be strict.
@inputs = $form->inputs
This method returns the list of inputs in the form. If called in
scalar context it returns the number of inputs contained in the
form. See "INPUTS" for what methods are available for the input
objects returned.
$input = $form->find_input( $selector )
$input = $form->find_input( $selector, $type )
$input = $form->find_input( $selector, $type, $index )
@inputs = $form->find_input( $selector )
@inputs = $form->find_input( $selector, $type )
This method is used to locate specific inputs within the form. All
inputs that match the arguments given are returned. In scalar
context only the first is returned, or "undef" if none match.
If $selector is not "undef", then the input's name, id, class
attribute must match. A selector prefixed with '#' must match the
id attribute of the input. A selector prefixed with '.' matches
the class attribute. A selector prefixed with '^' or with no
prefix matches the name attribute.
If $type is not "undef", then the input must have the specified
type. The following type names are used: "text", "password",
"hidden", "textarea", "file", "image", "submit", "radio",
"checkbox" and "option".
The $index is the sequence number of the input matched where 1 is
the first. If combined with $name and/or $type, then it selects
the nth input with the given name and/or type.
$value = $form->value( $selector )
$form->value( $selector, $new_value )
The value() method can be used to get/set the value of some input.
If strict is enabled and no input has the indicated name, then this
method will croak.
If multiple inputs have the same name, only the first one will be
affected.
The call:
$form->value('foo')
is basically a short-hand for:
$form->find_input('foo')->value;
@names = $form->param
@values = $form->param( $name )
$form->param( $name, $value, ... )
$form->param( $name, \@values )
Alternative interface to examining and setting the values of the
form.
If called without arguments then it returns the names of all the
inputs in the form. The names will not repeat even if multiple
inputs have the same name. In scalar context the number of
different names is returned.
If called with a single argument then it returns the value or
values of inputs with the given name. If called in scalar context
only the first value is returned. If no input exists with the
given name, then "undef" is returned.
If called with 2 or more arguments then it will set values of the
named inputs. This form will croak if no inputs have the given
name or if any of the values provided does not fit. Values can
also be provided as a reference to an array. This form will allow
unsetting all values with the given name as well.
This interface resembles that of the param() function of the CGI
module.
$form->try_others( \&callback )
This method will iterate over all permutations of unvisited
enumerated values (<select>, <radio>, <checkbox>) and invoke the
callback for each. The callback is passed the $form as argument.
The return value from the callback is ignored and the try_others()
method itself does not return anything.
$request = $form->make_request
Will return an HTTP::Request object that reflects the current
setting of the form. You might want to use the click() method
instead.
$request = $form->click
$request = $form->click( $selector )
$request = $form->click( $x, $y )
$request = $form->click( $selector, $x, $y )
Will "click" on the first clickable input (which will be of type
"submit" or "image"). The result of clicking is an HTTP::Request
object that can then be passed to LWP::UserAgent if you want to
obtain the server response.
If a $selector is specified, we will click on the first clickable
input matching the selector, and the method will croak if no
matching clickable input is found. If $selector is not specified,
then it is ok if the form contains no clickable inputs. In this
case the click() method returns the same request as the
make_request() method would do. See description of the
find_input() method above for how the $selector is specified.
If there are multiple clickable inputs with the same name, then
there is no way to get the click() method of the "HTML::Form" to
click on any but the first. If you need this you would have to
locate the input with find_input() and invoke the click() method on
the given input yourself.
A click coordinate pair can also be provided, but this only makes a
difference if you clicked on an image. The default coordinate is
(1,1). The upper-left corner of the image is (0,0), but some badly
coded CGI scripts are known to not recognize this. Therefore (1,1)
was selected as a safer default.
@kw = $form->form
Returns the current setting as a sequence of key/value pairs. Note
that keys might be repeated, which means that some values might be
lost if the return values are assigned to a hash.
In scalar context this method returns the number of key/value pairs
generated.
$form->dump
Returns a textual representation of current state of the form.
Mainly useful for debugging. If called in void context, then the
dump is printed on STDERR.
INPUTS
An "HTML::Form" objects contains a sequence of inputs. References to
the inputs can be obtained with the $form->inputs or $form->find_input
methods.
Note that there is not a one-to-one correspondence between input
objects and <input> elements in the HTML document. An input object
basically represents a name/value pair, so when multiple HTML elements
contribute to the same name/value pair in the submitted form they are
combined.
The input elements that are mapped one-to-one are "text", "textarea",
"password", "hidden", "file", "image", "submit" and "checkbox". For
the "radio" and "option" inputs the story is not as simple: All <input
type="radio"> elements with the same name will contribute to the same
input radio object. The number of radio input objects will be the same
as the number of distinct names used for the <input type="radio">
elements. For a <select> element without the "multiple" attribute
there will be one input object of type of "option". For a <select
multiple> element there will be one input object for each contained
<option> element. Each one of these option objects will have the same
name.
The following methods are available for the input objects:
$input->type
Returns the type of this input. The type is one of the following
strings: "text", "password", "hidden", "textarea", "file", "image",
"submit", "radio", "checkbox" or "option".
$name = $input->name
$input->name( $new_name )
This method can be used to get/set the current name of the input.
$input->id
$input->class
These methods can be used to get/set the current id or class
attribute for the input.
$input->selected( $selector )
Returns TRUE if the given selector matched the input. See the
description of the find_input() method above for a description of
the selector syntax.
$value = $input->value
$input->value( $new_value )
This method can be used to get/set the current value of an input.
If strict is enabled and the input only can take an enumerated list
of values, then it is an error to try to set it to something else
and the method will croak if you try.
You will also be able to set the value of read-only inputs, but a
warning will be generated if running under "perl -w".
$autocomplete = $input->autocomplete
$input->autocomplete( $new_autocomplete )
This method can be used to get/set the current value (if any) of
"autcomplete" for the input.
$input->possible_values
Returns a list of all values that an input can take. For inputs
that do not have discrete values, this returns an empty list.
$input->other_possible_values
Returns a list of all values not tried yet.
$input->value_names
For some inputs the values can have names that are different from
the values themselves. The number of names returned by this method
will match the number of values reported by
$input->possible_values.
When setting values using the value() method it is also possible to
use the value names in place of the value itself.
$bool = $input->readonly
$input->readonly( $bool )
This method is used to get/set the value of the readonly attribute.
You are allowed to modify the value of readonly inputs, but setting
the value will generate some noise when warnings are enabled.
Hidden fields always start out readonly.
$bool = $input->disabled
$input->disabled( $bool )
This method is used to get/set the value of the disabled attribute.
Disabled inputs do not contribute any key/value pairs for the form
value.
$input->form_name_value
Returns a (possible empty) list of key/value pairs that should be
incorporated in the form value from this input.
$input->check
Some input types represent toggles that can be turned on/off. This
includes "checkbox" and "option" inputs. Calling this method turns
this input on without having to know the value name. If the input
is already on, then nothing happens.
This has the same effect as:
$input->value($input->possible_values[1]);
The input can be turned off with:
$input->value(undef);
$input->click($form, $x, $y)
Some input types (currently "submit" buttons and "images") can be
clicked to submit the form. The click() method returns the
corresponding HTTP::Request object.
If the input is of type "file", then it has these additional methods:
$input->file
This is just an alias for the value() method. It sets the filename
to read data from.
For security reasons this field will never be initialized from the
parsing of a form. This prevents the server from triggering
stealth uploads of arbitrary files from the client machine.
$filename = $input->filename
$input->filename( $new_filename )
This get/sets the filename reported to the server during file
upload. This attribute defaults to the value reported by the
file() method.
$content = $input->content
$input->content( $new_content )
This get/sets the file content provided to the server during file
upload. This method can be used if you do not want the content to
be read from an actual file.
@headers = $input->headers
input->headers($key => $value, .... )
This get/set additional header fields describing the file uploaded.
This can for instance be used to set the "Content-Type" reported
for the file.
SEE ALSO
LWP(3), LWP::UserAgent(3), HTML::Parser(3)
AUTHOR
Gisle Aas <gisle@activestate.com>
COPYRIGHT AND LICENSE
This software is copyright (c) 1998 by Gisle Aas.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
perl v5.28.2 2020-02-21 HTML::Form(3)
html-form 6.70.0 - Generated Sun Feb 23 07:47:28 CST 2020