# View Helpers

In your view scripts, often it is necessary to perform certain complex functions over and over: e.g., formatting a date, generating form elements, or displaying action links. You can use helper classes to perform these behaviors for you.

A helper is simply a class. Let's say we want a helper named 'fooBar'. By default, the class is prefixed with 'Zend_View_Helper_' (you can specify a custom prefix when setting a helper path), and the last segment of the class name is the helper name; this segment should be TitleCapped; the full class name is then: `Zend_View_Helper_FooBar`. This class should contain at the minimum a single method, named after the helper, and camelCased: `fooBar()`.

## Watch the Case

Helper names are always camelCased, i.e., they never begin with an uppercase character. The class name itself is MixedCased, but the method that is actually executed is camelCased.

## Default Helper Path

The default helper path always points to the Zend Framework view helpers, i.e., 'Zend/View/Helper/'. Even if you call `setHelperPath()` to overwrite the existing paths, this path will be set to ensure the default helpers work.

To use a helper in your view script, call it using `$this->helperName()`. Behind the scenes, `Zend_View` will load the `Zend_View_Helper_HelperName` class, create an object instance of it, and call its `helperName()` method. The object instance is persistent within the `Zend_View` instance, and is reused for all future calls to `$this->helperName()`.

## Initial Helpers

`Zend_View` comes with an initial set of helper classes, most of which relate to form element generation and perform the appropriate output escaping automatically. In addition, there are helpers for creating route-based URLs and HTML lists, as well as declaring variables. The currently shipped helpers include:

- `declareVars()`: Primarily for use when using `strictVars()`, this helper can be used to declare template variables that may or may not already be set in the view object, as well as to set default values. Arrays passed as arguments to the method will be used to set default values; otherwise, if the variable does not exist, it is set to an empty string.

- `fieldset($name, $content, $attribs)`: Creates an XHTML fieldset. If `$attribs` contains a 'legend' key, that value will be used for the fieldset legend. The fieldset will surround the `$content` as provided to the helper.

- `form($name, $attribs, $content)`: Generates an XHTML form. All `$attribs` are escaped and rendered as XHTML attributes of the form tag. If `$content` is present and not a boolean `FALSE`, then that content is rendered within the start and close form tags; if `$content` is a boolean `FALSE` (the default), only the opening form tag is generated.

- `formButton($name, $value, $attribs)`: Creates an <button /> element.

- `formCheckbox($name, $value, $attribs, $options)`: Creates an <input type="checkbox" /> element.

  By default, when no $value is provided and no $options are present, '0' is assumed to be the unchecked value, and '1' the checked value. If a $value is passed, but no $options are present, the checked value is assumed to be the value passed. The unchecked value is implemented by rendering a hidden input element before rendering the checkbox.

  $options should be an array. If the array is indexed, the first value is the checked value, and the second the unchecked value; all other values are ignored. You may also pass an associative array with the keys 'checked' and 'unChecked'. The key 'disableHidden' can be set to true to prevent rendering of the hidden field for the unchecked value.

  If $options has been passed, if $value matches the checked value, then the element will be marked as checked. You may also mark the element as checked or unchecked by passing a boolean value for the attribute 'checked'.

  The above is probably best summed up with some examples:

      // '1' and '0' as checked/unchecked options; not checked
      echo $this->formCheckbox('foo');

      // '1' and '0' as checked/unchecked options; checked
      echo $this->formCheckbox('foo', null, array('checked' => true));

      // 'bar' and '0' as checked/unchecked options; not checked
      echo $this->formCheckbox('foo', 'bar');

      // 'bar' and '0' as checked/unchecked options; checked
      echo $this->formCheckbox('foo', 'bar', array('checked' => true));

      // 'bar' and 'baz' as checked/unchecked options; unchecked
      echo $this->formCheckbox('foo', null, null, array('bar', 'baz'));

      // 'bar' and 'baz' as checked/unchecked options; unchecked
      echo $this->formCheckbox('foo', null, null, array(
          'checked' => 'bar',
          'unChecked' => 'baz'
      ));

      // 'bar' and 'baz' as checked/unchecked options; checked
      echo $this->formCheckbox('foo', 'bar', null, array('bar', 'baz'));
      echo $this->formCheckbox('foo',
                               null,
                               array('checked' => true),
                               array('bar', 'baz'));

      // 'bar' and 'baz' as checked/unchecked options; unchecked
      echo $this->formCheckbox('foo', 'baz', null, array('bar', 'baz'));
      echo $this->formCheckbox('foo',
                               null,
                               array('checked' => false),
                               array('bar', 'baz'));

  In all cases, the markup prepends a hidden element with the unchecked value; this way, if the value is unchecked, you will still get a valid value returned to your form.

- `formErrors($errors, $options)`: Generates an XHTML unordered list to show errors. `$errors` should be a string or an array of strings; `$options` should be any attributes you want placed in the opening list tag.

  You can specify alternate opening, closing, and separator content when rendering the errors by calling several methods on the helper:

  - `setElementStart($string)`; default is '<ul class="errors"%s"><li>', where %s is replaced with the attributes as specified in `$options`.

  - `setElementSeparator($string)`; default is '</li><li>'.

  - `setElementEnd($string)`; default is '</li></ul>'.

- `formFile($name, $attribs)`: Creates an <input type="file" /> element.

- `formHidden($name, $value, $attribs)`: Creates an <input type="hidden" /> element.

- `formImage($name, $value, $attribs)`: Creates an <input type="image" /> element.

      echo $this->formImage(
          'foo',
          'bar',
          array(
              'src' => 'images/button.png',
              'alt' => 'Button',
          )
      );
      // Output: <input type="image" name="foo" id="foo" src="images/button.png" value="bar" alt="Button" />

- `formLabel($name, $value, $attribs)`: Creates a <label> element, setting the for attribute to `$name`, and the actual label text to `$value`. If disable is passed in attribs, nothing will be returned.

- `formMultiCheckbox($name, $value, $attribs, $options, $listsep)`: Creates a list of checkboxes. `$options` should be an associative array, and may be arbitrarily deep. `$value` may be a single value or an array of selected values that match the keys in the `$options` array. `$listsep` is an HTML break ("<br />") by default. By default, this element is treated as an array; all checkboxes share the same name, and are submitted as an array.

      // Using list separator ($listsep):

      echo '<ul><li>';
      echo $view->formMultiCheckbox(
          'foo',
          2,
          array(
              'class' => 'baz',
          ),
          array(
              1 => 'One',
              2 => 'Two',
              3 => 'Three',
          ),
          "</li>\n<li>"
      );
      echo '</li></ul>';

      /*
      Output:
      <ul>
          <li>
              <label for="foo-1">
                  <input type="checkbox" name="foo[]" id="foo-1" value="1" class="baz" />One
              </label>
          </li>
          <li>
              <label for="foo-2">
                  <input type="checkbox" name="foo[]" id="foo-2" value="2" checked="checked" class="baz" />Two
              </label>
          </li>
          <li>
              <label for="foo-3">
                  <input type="checkbox" name="foo[]" id="foo-3" value="3" class="baz" />Three</label>
              </li>
          </ul>
      */

      // Using options for label elements:
      echo $this->formMultiCheckbox(
          'foo',
          2,
          array(
              'label_placement' => 'prepend',
              'label_class'     => 'baz',
          ),
          array(
              1 => 'One',
              2 => 'Two',
              3 => 'Three',
          )
      );

      /*
      Output:
      <label class="baz" for="foo-1">
          One<input type="checkbox" name="foo[]" id="foo-1" value="1" />
      </label>
      <br />
      <label class="baz" for="foo-2">
          Two<input type="checkbox" name="foo[]" id="foo-2" value="2" checked="checked" />
      </label>
      <br />
      <label class="baz" for="foo-3">
          Three<input type="checkbox" name="foo[]" id="foo-3" value="3" />
      </label>
      */

- `formNote($name, $value = null)`: Creates a simple text note. (e.g. as element for headlines in a `Zend_Form` object)

      echo $this->formNote(null, 'This is an example text.');
      // Output: This is an example text.

- `formPassword($name, $value, $attribs)`: Creates an <input type="password" /> element.

- `formRadio($name, $value, $attribs, $options, $listsep)`: Creates a series of <input type="radio" /> elements, one for each of the $options elements. In the $options array, the element key is the radio value, and the element value is the radio label. The $value radio will be preselected for you.

      // Using list separator ($listsep)

      echo '<ul><li>';
      echo $this->formRadio(
          'foo',
          2,
          array(
              'class' => 'baz',
          ),
          array(
              1 => 'One',
              2 => 'Two',
              3 => 'Three',
          ),
          "</li>\n<li>"
      );
      echo '</li></ul>';

      /*
      Output:
      <ul>
          <li>
              <label for="foo-1">
                  <input type="radio" name="foo" id="foo-1" value="1" class="baz" />One
              </label>
          </li>
          <li>
              <label for="foo-2">
                  <input type="radio" name="foo" id="foo-2" value="2" checked="checked" class="baz" />Two
              </label>
          </li>
          <li>
              <label for="foo-3">
                  <input type="radio" name="foo" id="foo-3" value="3" class="baz" />Three
              </label>
          </li>
      </ul>
      */

      // Using options for label elements:

      echo $this->formRadio(
          'foo',
          2,
          array(
              'label_placement' => 'prepend',
              'label_class'     => 'baz',
          ),
          array(
              1 => 'One',
              2 => 'Two',
              3 => 'Three',
          )
      );

      /*
      Output:
      <label class="baz" for="foo-1">
          One<input type="radio" name="foo" id="foo-1" value="1" />
      </label>
      <br />
      <label class="baz" for="foo-2">
          Two<input type="radio" name="foo" id="foo-2" value="2" checked="checked" />
      </label>
      <br />
      <label class="baz" for="foo-3">
          Three<input type="radio" name="foo" id="foo-3" value="3" />
      </label>
      */

- `formReset($name, $value, $attribs)`: Creates an <input type="reset" /> element.

- `formSelect($name, $value, $attribs, $options)`: Creates a <select>...</select> block, with one <option>one for each of the $options elements. In the $options array, the element key is the option value, and the element value is the option label. The $value option(s) will be preselected for you.

      // Using option groups:

      echo $view->formSelect(
          'foo',
          2,
          array(
              'class' => 'baz',
          ),
          array(
              1     => 'One',
              'Two' => array(
                  '2.1' => 'One',
                  '2.2' => 'Two',
                  '2.3' => 'Three',
              ),
              3     => 'Three',
          )
      );

      /*
      Output:
      <select name="foo" id="foo" class="baz">
          <option value="1" label="One">One</option>
          <optgroup id="foo-optgroup-Two" label="Two">
              <option value="2.1" label="One">One</option>
              <option value="2.2" label="Two">Two</option>
              <option value="2.3" label="Three">Three</option>
          </optgroup>
          <option value="3" label="Three">Three</option>
      </select>
      */

      // First example with 'multiple' option:

      echo $this->formSelect(
          'foo[]',
          2,
          null,
          array(
              1 => 'One',
              2 => 'Two',
              3 => 'Three',
          )
      );

      /*
      Output:
      <select name="foo[]" id="foo" multiple="multiple">
          <option value="1" label="One">One</option>
          <option value="2" label="Two" selected="selected">Two</option>
          <option value="3" label="Three">Three</option>
      </select>
      */

      // Second example with 'multiple' option:

      echo $this->formSelect(
          'foo',
          array(
              1,
              2,
          ),
          array(
              'multiple' => true,
          ),
          array(
              1 => 'One',
              2 => 'Two',
              3 => 'Three',
          )
      );

      /*
      Output:
      <select name="foo[]" id="foo" multiple="multiple">
          <option value="1" label="One" selected="selected">One</option>
          <option value="2" label="Two" selected="selected">Two</option>
          <option value="3" label="Three">Three</option>
      </select>
      */

- `formSubmit($name, $value, $attribs)`: Creates an <input type="submit" /> element.

- `formText($name, $value, $attribs)`: Creates an <input type="text" /> element.

- `formTextarea($name, $value, $attribs)`: Creates a <textarea>...</textarea> block.

- `url($urlOptions, $name, $reset, $encode)`: Creates a URL string based on a named route. `$urlOptions` should be an associative array of key/value pairs used by the particular route.

      // Using without options: (current request is: user/id/1)
      echo $this->url();
      // Output: user/info/id/1

      // Set URL options:
      echo $this->url(
          array('controller' => 'user', 'action' => 'info', 'username' => 'foobar')
      );
      // Output: user/info/username/foobar

      // Using a route:
      $router->addRoute(
          'user',
          new Zend_Controller_Router_Route(
              'user/:username',
              array(
                  'controller' => 'user',
                  'action'     => 'info',
              )
          )
      );

      echo $this->url(array('name' => 'foobar'), 'user');
      // Output: user/foobar

      // Using reset: (current request is: user/id/1)
      echo $this->url(array('controller' => 'user', 'action' => 'info'), null, false);
      // Output: user/info/id/1

      echo $this->url(array('controller' => 'user', 'action' => 'info'), null, true);
      // Output: user/info

      // Using encode:
      echo $this->url(
          array('controller' => 'user', 'action' => 'info', 'username' => 'John Doe'), null, true, false
      );
      // Output: user/info/username/John Doe

      echo $this->url(
          array('controller' => 'user', 'action' => 'info', 'username' => 'John Doe'), null, true, false
      );
      // Output: user/info/username/John+Doe

- `serverUrl($requestUri = null)`: Helper for returning the current server URL (optionally with request URI).

      // Current server URL in the example is: http://www.example.com/foo.html

      echo $this->serverUrl();
      // Output: http://www.example.com

      echo $this->serverUrl(true);
      // Output: http://www.example.com/foo.html

      echo $this->serverUrl('/foo/bar');
      // Output: http://www.example.com/foo/bar

      echo $this->serverUrl()->getHost();
      // Output: www.example.com

      echo $this->serverUrl()->getScheme();
      // Output: http

      $this->serverUrl()->setHost('www.foo.com');
      $this->serverUrl()->setScheme('https');
      echo $this->serverUrl();
      // Output: https://www.foo.com

- `htmlList($items, $ordered, $attribs, $escape)`: generates unordered and ordered lists based on the `$items` passed to it. If `$items` is a multidimensional array, a nested list will be built. If the `$escape` flag is `TRUE` (default), individual items will be escaped using the view objects registered escaping mechanisms; pass a `FALSE` value if you want to allow markup in your lists.

Using these in your view scripts is very easy, here is an example. Note that you all you need to do is call them; they will load and instantiate themselves as they are needed.

    // inside your view script, $this refers to the Zend_View instance.
    //
    // say that you have already assigned a series of select options under
    // the name $countries as array('us' => 'United States', 'il' =>
    // 'Israel', 'de' => 'Germany').
    ?>
    <form action="action.php" method="post">
        <p><label>Your Email:
    <?php echo $this->formText('email', 'you@example.com', array('size' => 32)) ?>
        </label></p>
        <p><label>Your Country:
    <?php echo $this->formSelect('country', 'us', null, $this->countries) ?>
        </label></p>
        <p><label>Would you like to opt in?
    <?php echo $this->formCheckbox('opt_in', 'yes', null, array('yes', 'no')) ?>
        </label></p>
    </form>

The resulting output from the view script will look something like this:

    <form action="action.php" method="post">
        <p><label>Your Email:
            <input type="text" name="email" value="you@example.com" size="32" />
        </label></p>
        <p><label>Your Country:
            <select name="country">
                <option value="us" selected="selected">United States</option>
                <option value="il">Israel</option>
                <option value="de">Germany</option>
            </select>
        </label></p>
        <p><label>Would you like to opt in?
            <input type="hidden" name="opt_in" value="no" />
            <input type="checkbox" name="opt_in" value="yes" checked="checked" />
        </label></p>
    </form>

## Helper Paths

As with view scripts, your controller can specify a stack of paths for `Zend_View` to search for helper classes. By default, `Zend_View` looks in "Zend/View/Helper/*" for helper classes. You can tell `Zend_View` to look in other locations using the `setHelperPath()` and `addHelperPath()` methods. Additionally, you can indicate a class prefix to use for helpers in the path provided, to allow namespacing your helper classes. By default, if no class prefix is provided, 'Zend_View_Helper_' is assumed.

    $view = new Zend_View();

    // Set path to /path/to/more/helpers, with prefix 'My_View_Helper'
    $view->setHelperPath('/path/to/more/helpers', 'My_View_Helper');

In fact, you can "stack" paths using the `addHelperPath()` method. As you add paths to the stack, `Zend_View` will look at the most-recently-added path for the requested helper class. This allows you to add to (or even override) the initial distribution of helpers with your own custom helpers.

    $view = new Zend_View();
    // Add /path/to/some/helpers with class prefix 'My_View_Helper'
    $view->addHelperPath('/path/to/some/helpers', 'My_View_Helper');
    // Add /other/path/to/helpers with class prefix 'Your_View_Helper'
    $view->addHelperPath('/other/path/to/helpers', 'Your_View_Helper');

    // now when you call $this->helperName(), Zend_View will look first for
    // "/path/to/some/helpers/HelperName" using class name
    // "Your_View_Helper_HelperName", then for
    // "/other/path/to/helpers/HelperName.php" using class name
    // "My_View_Helper_HelperName", and finally for
    // "Zend/View/Helper/HelperName.php" using class name
    // "Zend_View_Helper_HelperName".

## Writing Custom Helpers

Writing custom helpers is easy; just follow these rules:

- While not strictly necessary, we recommend either implementing `Zend_View_Helper_Interface` or extending `Zend_View_Helper_Abstract` when creating your helpers. Introduced in 1.6.0, these simply define a `setView()` method; however, in upcoming releases, we plan to implement a strategy pattern that will simplify much of the naming schema detailed below. Building off these now will help you future-proof your code.

- The class name must, at the very minimum, end with the helper name itself, using MixedCaps. E.g., if you were writing a helper called "specialPurpose", the class name would minimally need to be "SpecialPurpose". You may, and should, give the class name a prefix, and it is recommended that you use 'View_Helper' as part of that prefix: "My_View_Helper_SpecialPurpose". (You will need to pass in the prefix, with or without the trailing underscore, to `addHelperPath()` or `setHelperPath()`).

- The class must have a public method that matches the helper name; this is the method that will be called when your template calls "$this->specialPurpose()". In our "specialPurpose" helper example, the required method declaration would be "public function specialPurpose()".

- In general, the class should not echo or print or otherwise generate output. Instead, it should return values to be printed or echoed. The returned values should be escaped appropriately.

- The class must be in a file named after the helper class. Again using our "specialPurpose" helper example, the file has to be named "SpecialPurpose.php".

Place the helper class file somewhere in your helper path stack, and `Zend_View` will automatically load, instantiate, persist, and execute it for you.

Here is an example of our `SpecialPurpose` helper code:

    class My_View_Helper_SpecialPurpose extends Zend_View_Helper_Abstract
    {
        protected $_count = 0;
        public function specialPurpose()
        {
            $this->_count++;
            $output = "I have seen 'The Jerk' {$this->_count} time(s).";
            return htmlspecialchars($output);
        }
    }

Then in a view script, you can call the `SpecialPurpose` helper as many times as you like; it will be instantiated once, and then it persists for the life of that `Zend_View` instance.

    // remember, in a view script, $this refers to the Zend_View instance.
    echo $this->specialPurpose();
    echo $this->specialPurpose();
    echo $this->specialPurpose();

The output would look something like this:

    I have seen 'The Jerk' 1 time(s).
    I have seen 'The Jerk' 2 time(s).
    I have seen 'The Jerk' 3 time(s).

Sometimes you will need access to the calling `Zend_View` object -- for instance, if you need to use the registered encoding, or want to render another view script as part of your helper. To get access to the view object, your helper class should have a `setView($view)` method, like the following:

    class My_View_Helper_ScriptPath
    {
        public $view;

        public function setView(Zend_View_Interface $view)
        {
            $this->view = $view;
        }

        public function scriptPath($script)
        {
            return $this->view->getScriptPath($script);
        }
    }

If your helper class has a `setView()` method, it will be called when the helper class is first instantiated, and passed the current view object. It is up to you to persist the object in your class, as well as determine how it should be accessed.

If you are extending `Zend_View_Helper_Abstract`, you do not need to define this method, as it is defined for you.

## Registering Concrete Helpers

Sometimes it is convenient to instantiate a view helper, and then register it with the view. As of version 1.10.0, this is now possible using the `registerHelper()` method, which expects two arguments: the helper object, and the name by which it will be registered.

    $helper = new My_Helper_Foo();
    // ...do some configuration or dependency injection...

    $view->registerHelper($helper, 'foo');

If the helper has a `setView()` method, the view object will call this and inject itself into the helper on registration.

### Helper name should match a method

The second argument to `registerHelper()` is the name of the helper. A corresponding method name should exist in the helper; otherwise, `Zend_View` will call a non-existent method when invoking the helper, raising a fatal PHP error.