Zend_Form makes use of Zend_Loader_PluginLoader to allow developers to specify the locations of alternate elements and decorators. Each has its own plugin loader associated with it, and general accessors are used to retrieve and modify each.

The following loader types are used with the various plugin loader methods: 'element' and 'decorator'. The type names are case insensitive.

The methods used to interact with plugin loaders are as follows:

• setPluginLoader($loader, $type): $loader is the plugin loader object itself, while type is one of the types specified above. This sets the plugin loader for the given type to the newly specified loader object.

• getPluginLoader($type): retrieves the plugin loader associated with $type.

• addPrefixPath($prefix, $path, $type = null): adds a prefix/path association to the loader specified by $type. If $type is NULL, it will attempt to add the path to all loaders, by appending the prefix with each of "_Element" and "_Decorator"; and appending the path with "Element/" and "Decorator/". If you have all your extra form element classes under a common hierarchy, this is a convenience method for setting the base prefix for them.

• addPrefixPaths(array $spec): allows you to add many paths at once to one or more plugin loaders. It expects each array item to be an array with the keys 'path', 'prefix', and 'type'.

Additionally, you can specify prefix paths for all elements and display groups created through a Zend_Form instance using the following methods:

• addElementPrefixPath($prefix, $path, $type = null): Just like addPrefixPath(), you must specify a class prefix and a path. $type, when specified, must be one of the plugin loader types specified by Zend_Form_Element; see the element plugins section for more information on valid $type values. If no $type is specified, the method will assume it is a general prefix for all types.

• addDisplayGroupPrefixPath($prefix, $path): Just like addPrefixPath(), you must specify a class prefix and a path; however, since display groups only support decorators as plugins, no $type is necessary.

Custom elements and decorators are an easy way to share functionality between forms and encapsulate custom functionality. See the Custom Label example in the elements documentation for an example of how custom elements can be used as replacements for standard classes.

Zend_Form provides several accessors for adding and removing form elements from a form. These can take element object instances or serve as factories for instantiating the element objects themselves.

The most basic method for adding an element is addElement(). This method can take either an object of type Zend_Form_Element (or of a class extending Zend_Form_Element), or arguments for building a new element -- including the element type, name, and any configuration options.

Some examples:

Note: addElement() Implements Fluent Interface
addElement() implements a fluent interface; that is to say, it returns the Zend_Form object, and not the element. This is done to allow you to chain together multiple addElement() methods or other form methods that implement the fluent interface (all setters in Zend_Form implement the pattern).
If you wish to return the element instead, use createElement(), which is outlined below. Be aware, however, that createElement() does not attach the element to the form.
Internally, addElement() actually uses createElement() to create the element before attaching it to the form.

Once an element has been added to the form, you can retrieve it by name. This can be done either by using the getElement() method or by using overloading to access the element as an object property:

Occasionally, you may want to create an element without attaching it to the form (for instance, if you wish to make use of the various plugin paths registered with the form, but wish to later attach the object to a sub form). The createElement() method allows you to do so:

Display groups are a way to create virtual groupings of elements for display purposes. All elements remain accessible by name in the form, but when iterating over the form or rendering, any elements in a display group are rendered together. The most common use case for this is for grouping elements in fieldsets.

The base class for display groups is Zend_Form_DisplayGroup. While it can be instantiated directly, it is usually best to use Zend_Form's addDisplayGroup() method to do so. This method takes an array of element names as its first argument, and a name for the display group as its second argument. You may optionally pass in an array of options or a Zend_Config object as the third argument.

Assuming that the elements 'username' and 'password' are already set in the form, the following code would group these elements in a 'login' display group:

You can access display groups using the getDisplayGroup() method, or via overloading using the display group's name:

Note: Default Decorators Do Not Need to Be Loaded
By default, the default decorators are loaded during object initialization. You can disable this by passing the 'disableLoadDefaultDecorators' option when creating a display group:

1. $form->addDisplayGroup(
2.     array('foo', 'bar'),
3.     'foobar',
4.     array('disableLoadDefaultDecorators' => true)
5. );

This option may be mixed with any other options you pass, both as array options or in a Zend_Config object.

Sub forms serve several purposes:

• Creating logical element groups. Since sub forms are simply forms, you can validate subforms as individual entities.

• Creating multi-page forms. Since sub forms are simply forms, you can display a separate sub form per page, building up multi-page forms where each form has its own validation logic. Only once all sub forms validate would the form be considered complete.

• Display groupings. Like display groups, sub forms, when rendered as part of a larger form, can be used to group elements. Be aware, however, that the master form object will have no awareness of the elements in sub forms.

A sub form may be a Zend_Form object, or, more typically, a Zend_Form_SubForm object. The latter contains decorators suitable for inclusion in a larger form (i.e., it does not render additional HTML form tags, but does group elements). To attach a sub form, simply add it to the form and give it a name:

You can retrieve a sub form using either getSubForm($name) or overloading using the sub form name:

Sub forms are included in form iteration, although the elements they contain are not.

While a form's usefulness primarily derives from the elements it contains, it can also contain other metadata, such as a name (often used as a unique ID in the HTML markup); the form action and method; the number of elements, groups, and sub forms it contains; and arbitrary metadata (usually used to set HTML attributes for the form tag itself).

You can set and retrieve a form's name using the name accessors:

To set the action (url to which the form submits) and method (method by which it should submit, e.g., 'POST' or 'GET'), use the action and method accessors:

You may also specify the form encoding type specifically using the enctype accessors. Zend_Form defines two constants, Zend_Form::ENCTYPE_URLENCODED and Zend_Form::ENCTYPE_MULTIPART, corresponding to the values 'application/x-www-form-urlencoded' and 'multipart/form-data', respectively; however, you can set this to any arbitrary encoding type.

Note: The method, action, and enctype are only used internally for rendering, and not for any sort of validation.

Zend_Form implements the Countable interface, allowing you to pass it as an argument to count:

Setting arbitrary metadata is done through the attribs accessors. Since overloading in Zend_Form is used to access elements, display groups, and sub forms, this is the only method for accessing metadata.

Creating the markup for a form is often a time-consuming task, particularly if you plan on re-using the same markup to show things such as validation errors, submitted values, etc. Zend_Form's answer to this issue is decorators.

Decorators for Zend_Form objects can be used to render a form. The FormElements decorator will iterate through all items in a form -- elements, display groups, and sub forms -- and render them, returning the result. Additional decorators may then be used to wrap this content, or append or prepend it.

The default decorators for Zend_Form are FormElements, HtmlTag (wraps in a definition list), and Form; the equivalent code for creating them is as follows:

This creates output like the following:

Any attributes set on the form object will be used as HTML attributes of the <form> tag.

Note: Default Decorators Do Not Need to Be Loaded
By default, the default decorators are loaded during object initialization. You can disable this by passing the 'disableLoadDefaultDecorators' option to the constructor:

1. $form = new Zend_Form(array('disableLoadDefaultDecorators' => true));

This option may be mixed with any other options you pass, both as array options or in a Zend_Config object.

Note: Using Multiple Decorators of the Same Type
Internally, Zend_Form uses a decorator's class as the lookup mechanism when retrieving decorators. As a result, you cannot register multiple decorators of the same type; subsequent decorators will simply overwrite those that existed before.
To get around this, you can use aliases. Instead of passing a decorator or decorator name as the first argument to addDecorator(), pass an array with a single element, with the alias pointing to the decorator object or name:

1. // Alias to 'FooBar':
2. $form->addDecorator(array('FooBar' => 'HtmlTag'), array('tag' => 'div'));
3.  
4. // And retrieve later:
5. $form = $element->getDecorator('FooBar');

In the addDecorators() and setDecorators() methods, you will need to pass the 'decorator' option in the array representing the decorator:

1. // Add two 'HtmlTag' decorators, aliasing one to 'FooBar':
2. $form->addDecorators(
3.     array('HtmlTag', array('tag' => 'div')),
4.     array(
5.         'decorator' => array('FooBar' => 'HtmlTag'),
6.         'options' => array('tag' => 'dd')
7.     ),
8. );
9.  
10. // And retrieve later:
11. $htmlTag = $form->getDecorator('HtmlTag');
12. $fooBar  = $form->getDecorator('FooBar');

You may create your own decorators for generating the form. One common use case is if you know the exact HTML you wish to use; your decorator could create the exact HTML and simply return it, potentially using the decorators from individual elements or display groups.

The following methods may be used to interact with decorators:

• addDecorator($decorator, $options = null)

• addDecorators(array $decorators)

• setDecorators(array $decorators)

• getDecorator($name)

• getDecorators()

• removeDecorator($name)

• clearDecorators()

Zend_Form also uses overloading to allow rendering specific decorators. __call() will intercept methods that lead with the text 'render' and use the remainder of the method name to lookup a decorator; if found, it will then render that single decorator. Any arguments passed to the method call will be used as content to pass to the decorator's render() method. As an example:

If the decorator does not exist, an exception is raised.

A primary use case for forms is validating submitted data. Zend_Form allows you to validate an entire form, a partial form, or responses for XmlHttpRequests (AJAX). If the submitted data is not valid, it has methods for retrieving the various error codes and messages for elements and sub forms.

To validate a full form, use the isValid() method:

isValid() will validate every required element, and any unrequired element contained in the submitted data.

Sometimes you may need to validate only a subset of the data; for this, use isValidPartial($data):

isValidPartial() only attempts to validate those items in the data for which there are matching elements; if an element is not represented in the data, it is skipped.

When validating elements or groups of elements for an AJAX request, you will typically be validating a subset of the form, and want the response back in JSON. processAjax() does precisely that:

You can then simply send the JSON response to the client. If the form is valid, this will be a boolean TRUE response. If not, it will be a javascript object containing key/message pairs, where each 'message' is an array of validation error messages.

For forms that fail validation, you can retrieve both error codes and error messages, using getErrors() and getMessages(), respectively:

Note: Since the messages returned by getMessages() are an array of error code/message pairs, getErrors() is typically not needed.

You can retrieve codes and error messages for individual elements by simply passing the element name to each:

Note: Note: When validating elements, Zend_Form sends a second argument to each element's isValid() method: the array of data being validated. This can then be used by individual validators to allow them to utilize other submitted values when determining the validity of the data. An example would be a registration form that requires both a password and password confirmation; the password element could use the password confirmation as part of its validation.

The following is a full list of methods available to Zend_Form, grouped by type:

• Configuration and Options:

  • setOptions(array $options)

  • setConfig(Zend_Config $config)

• Plugin Loaders and paths:

  • setPluginLoader(Zend_Loader_PluginLoader_Interface $loader, $type = null)

  • getPluginLoader($type = null)

  • addPrefixPath($prefix, $path, $type = null)

  • addPrefixPaths(array $spec)

  • addElementPrefixPath($prefix, $path, $type = null)

  • addElementPrefixPaths(array $spec)

  • addDisplayGroupPrefixPath($prefix, $path)

• Metadata:

  • setAttrib($key, $value)

  • addAttribs(array $attribs)

  • setAttribs(array $attribs)

  • getAttrib($key)

  • getAttribs()

  • removeAttrib($key)

  • clearAttribs()

  • setAction($action)

  • getAction()

  • setMethod($method)

  • getMethod()

  • setName($name)

  • getName()

• Elements:

  • addElement($element, $name = null, $options = null)

  • addElements(array $elements)

  • setElements(array $elements)

  • getElement($name)

  • getElements()

  • removeElement($name)

  • clearElements()

  • setDefaults(array $defaults)

  • setDefault($name, $value)

  • getValue($name)

  • getValues()

  • getUnfilteredValue($name)

  • getUnfilteredValues()

  • setElementFilters(array $filters)

  • setElementDecorators(array $decorators)

• Sub forms:

  • addSubForm(Zend_Form $form, $name, $order = null)

  • addSubForms(array $subForms)

  • setSubForms(array $subForms)

  • getSubForm($name)

  • getSubForms()

  • removeSubForm($name)

  • clearSubForms()

  • setSubFormDecorators(array $decorators)

• Display groups:

  • addDisplayGroup(array $elements, $name, $options = null)

  • addDisplayGroups(array $groups)

  • setDisplayGroups(array $groups)

  • getDisplayGroup($name)

  • getDisplayGroups()

  • removeDisplayGroup($name)

  • clearDisplayGroups()

  • setDisplayGroupDecorators(array $decorators)

• Validation

  • populate(array $values)

  • isValid(array $data)

  • isValidPartial(array $data)

  • processAjax(array $data)

  • persistData()

  • getErrors($name = null)

  • getMessages($name = null)

• Rendering:

  • setView(Zend_View_Interface $view = null)

  • getView()

  • addDecorator($decorator, $options = null)

  • addDecorators(array $decorators)

  • setDecorators(array $decorators)

  • getDecorator($name)

  • getDecorators()

  • removeDecorator($name)

  • clearDecorators()

  • render(Zend_View_Interface $view = null)

• I18n:

  • setTranslator(Zend_Translate_Adapter $translator = null)

  • getTranslator()

  • setDisableTranslator($flag)

  • translatorIsDisabled()

Zend_Form is fully configurable via setOptions() and setConfig() (or by passing options or a Zend_Config object to the constructor). Using these methods, you can specify form elements, display groups, decorators, and metadata.

As a general rule, if 'set' + the option key refers to a Zend_Form method, then the value provided will be passed to that method. If the accessor does not exist, the key is assumed to reference an attribute, and will be passed to setAttrib().

Exceptions to the rule include the following:

• prefixPath will be passed to addPrefixPaths()

• elementPrefixPath will be passed to addElementPrefixPaths()

• displayGroupPrefixPath will be passed to addDisplayGroupPrefixPaths()

• the following setters cannot be set in this way:

  • setAttrib (though setAttribs *will* work)

  • setConfig

  • setDefault

  • setOptions

  • setPluginLoader

  • setSubForms

  • setTranslator

  • setView

As an example, here is a config file that passes configuration for every type of configurable data:

The above could easily be abstracted to an XML or PHP array-based configuration file.

An alternative to using configuration-based forms is to subclass Zend_Form. This has several benefits:

• You can unit test your form easily to ensure validations and rendering perform as expected.

• Fine-grained control over individual elements.

• Re-use of form objects, and greater portability (no need to track config files).

• Implementing custom functionality.

The most typical use case would be to use the init() method to setup specific form elements and configuration:

This form can then be instantiated with simply:

and all functionality is already setup and ready; no config files needed. (Note that this example is greatly simplified, as it contains no validators or filters for the elements.)

Another common reason for extension is to define a set of default decorators. You can do this by overriding the loadDefaultDecorators() method: