Hi All,
Pardon the cross-post but I thought this was important enough to make sure
it got to all the necessary places. Some of you may have noticed a new form
package in the Joomla 1.6 trunk. The new form package provides a robust API
for creating, populating, filtering, and validating form data via XML and
PHP. The forms are created with XML similar to JParameter but JForm  is
powerful enough to be used for a complete form, not just a set of
parameters.

Filtering

By defining a filter attribute on each form field, JForm will allow you to
completely sanitize your form input with one API call. The filter attribute
will accept a variety of values including "unset" for read only data,
"safehtml" for limited HTML support, "raw" for full HTML support, all
JFilterInput::clean() mechanisms including "integer", "boolean", "base64",
etc. as well as callbacks in the form of "my_callback_method" or
"JFilterOutput::stringUrlSafe".

Validation

By defining a validate attribute for each form field, JForm will also
validate form data. Some simple rules are available right now but there will
probably be more coming in the near future. To validate an e-mail address,
you can use validate="email" and the e-mail validator takes an optional
attribute unique="unique" which will validate that the e-mail address is not
in use by another user. If you use the unique option, you have to also
specify a key for the user's table. It is easy to build your own validation
rules and they can be combined to create some pretty sophisticated
validation logic.

For example:

<field
name="id"
type="hidden"
filter="integer"
/>

<field
name="email1"
type="text"
id="email1"
label="PROFILE FORM EMAIL1 LABEL"
description="PROFILE FORM EMAIL1 LABEL"
message="PROFILE FORM EMAIL1 MESSAGE"
class="inputbox validate-email"
size="30"
default=""
required="true"
filter="string"
validate="email"
field="id"
unique="true"
/>

<field
name="email2"
type="text"
id="email2"
label="PROFILE FORM EMAIL2 LABEL"
description="PROFILE FORM EMAIL2 LABEL"
message="PROFILE FORM EMAIL2 MESSAGE"
class="inputbox validate-email"
size="30"
default=""
required="true"
filter="string"
validate="equals"
field="email1"
/>

The field definitions could be used in a user data edit screen to ensure
that the user's e-mail address is unique to that user and that the email1
and email2 fields match. The email1 field will validate that the e-mail
address is unique to the user and the email2 field will verify that it's
supplied value matches the value given to email1. You can also specify
custom validation messages via the message attribute.

Getting A Form

Let's assume you have an MVC component with a "forms" folder within the
"models" folder. In the forms folder, you have a form file named
"profile.xml". To get a instance of the form you would do something like:

// Get the form.
jimport('joomla.form.form');
JForm::addFormPath(JPATH_COMPONENT.DS.'models'.DS.'forms');
$form = &JForm::getInstance('jform', 'profile', true, array('array' =>
true));

JForm::addFormPath() works similarly to JModel::addIncludePath or
JHtml::addIncludePath(). JForm::getInstance() returns a JForm instance. The
first parameter is a name to identify the form by and will come into play
when with the array option that you see in the forth parameter. The second
parameter, "profile", tells JForm where to get the XML data from and the
third option indicates that "profile" is a file name. Instead of specifying
a file name, you can pass in straight XML into the second parameter and set
the third parameter to false. The fourth parameter, array('array' => true),
tells JForm to render the individual field names as an array. If our
profile.xml contained the fields posted above, the field names would be
jform[id], jform[email1], and jform[email2]. If the array option is set to
false, the field names would be rendered as id, email1, and email2.

The array option is very convenient because it makes loading the form data
and running it through the filter/validator extremely quick.

// Get the form.
jimport('joomla.form.form');
JForm::addFormPath(JPATH_COMPONENT.DS.'models'.DS.'forms');
$form = &JForm::getInstance('jform', 'profile', true, array('array' =>
true));

// Get the profile data.
$data = JRequest::getVar('jform', array(), 'post', 'array');

// Filter and validate the form data.
$data = $form->filter($data);
$return = $form->validate($data);

// Check for errors and save...

Notes

* We are still sorting out some of the error handling and validation warning
feedback for PHP 5.2. The error handling will probably be updated in the
near future to make distinguishing hard errors from validation errors
easier.

* The library as a whole is quite powerful and I hope that it is fairly easy
to understand but it will probably require some trial and error to really
get the hang of. The newly committed com_weblinks admin component should
serve as a useful example of how to use the new form package and the access
control system will begin to use it more in the near future.

That is all I can think of right now but I'm sure I've probably forgot
something. If you guys have any questions, feel free to ask and I will do my
best to help you out.

Best,
Rob Schley