repo_zf1/documentation/manual/en/module_specs/Zend_View-Helpers.xml

<?xml version="1.0" encoding="UTF-8"?>
<!-- Reviewed: no -->
<sect1 id="zend.view.helpers" xmlns:xi="http://www.w3.org/2001/XInclude">
    <title>View Helpers</title>

    <para>
        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.
    </para>

    <para>
        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:
        <classname>Zend_View_Helper_FooBar</classname>. This class should contain at the
        minimum a single method, named after the helper, and camelCased:
        <methodname>fooBar()</methodname>.
    </para>

    <note>
        <title>Watch the Case</title>

        <para>
            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.
        </para>
    </note>

    <note>
        <title>Default Helper Path</title>

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

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

    <sect2 id="zend.view.helpers.initial">
        <title>Initial Helpers</title>

        <para>
            <classname>Zend_View</classname> 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 <acronym>URL</acronym>s and <acronym>HTML</acronym>
            lists, as well as declaring variables. The currently shipped helpers include:
        </para>

        <itemizedlist>
            <listitem>
                <para>
                    <methodname>declareVars()</methodname>: Primarily for use when using
                    <methodname>strictVars()</methodname>, 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.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>fieldset($name, $content, $attribs)</methodname>: Creates an
                    <acronym>XHTML</acronym> fieldset. If <varname>$attribs</varname> contains a
                    'legend' key, that value will be used for the fieldset legend. The
                    fieldset will surround the <varname>$content</varname> as provided to
                    the helper.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>form($name, $attribs, $content)</methodname>: Generates an
                    <acronym>XHTML</acronym> form. All <varname>$attribs</varname> are escaped and
                    rendered as <acronym>XHTML</acronym> attributes of the form tag. If
                    <varname>$content</varname> is present and not a boolean
                    <constant>FALSE</constant>, then that content is rendered within the start and
                    close form tags; if <varname>$content</varname> is a boolean
                    <constant>FALSE</constant> (the default), only the opening form tag is
                    generated.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>formButton($name, $value, $attribs)</methodname>: Creates an
                    &lt;button /&gt; element.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>formCheckbox($name, $value, $attribs, $options)</methodname>:
                    Creates an &lt;input type="checkbox" /&gt; element.
                </para>

                <para>
                    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.
                </para>

                <para>
                    $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.
                </para>

                <para>
                    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'.
                </para>

                <para>
                    The above is probably best summed up with some examples:
                </para>

                <programlisting language="php"><![CDATA[
// '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'));
]]></programlisting>

                <para>
                    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.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>formErrors($errors, $options)</methodname>: Generates an
                    <acronym>XHTML</acronym> unordered list to show errors.
                    <varname>$errors</varname> should be a string or an array of strings;
                    <varname>$options</varname> should be any attributes you want
                    placed in the opening list tag.
                </para>

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

                <itemizedlist>
                    <listitem>
                        <para>
                            <methodname>setElementStart($string)</methodname>; default is
                            '&lt;ul class="errors"%s"&gt;&lt;li&gt;', where %s
                            is replaced with the attributes as specified in
                            <varname>$options</varname>.
                        </para>
                    </listitem>

                    <listitem>
                        <para>
                            <methodname>setElementSeparator($string)</methodname>; default
                            is '&lt;/li&gt;&lt;li&gt;'.
                        </para>
                    </listitem>

                    <listitem>
                        <para>
                            <methodname>setElementEnd($string)</methodname>; default is
                            '&lt;/li&gt;&lt;/ul&gt;'.
                        </para>
                    </listitem>
                </itemizedlist>
            </listitem>

            <listitem>
                <para>
                    <methodname>formFile($name, $attribs)</methodname>: Creates an
                    &lt;input type="file" /&gt; element.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>formHidden($name, $value, $attribs)</methodname>: Creates an
                    &lt;input type="hidden" /&gt; element.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>formImage($name, $value, $attribs)</methodname>: Creates an
                    &lt;input type="image" /&gt; element.
                </para>

<programlisting language="php"><![CDATA[
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" />
]]></programlisting>
            </listitem>

            <listitem>
                <para>
                    <methodname>formLabel($name, $value, $attribs)</methodname>: Creates a
                    &lt;label&gt; element, setting the <property>for</property> attribute to
                    <varname>$name</varname>, and the actual label text to
                    <varname>$value</varname>. If <emphasis>disable</emphasis> is passed in
                    <property>attribs</property>, nothing will be returned.
                </para>
            </listitem>

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

<programlisting language="php"><![CDATA[
// 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>
*/
]]></programlisting>
            </listitem>

            <listitem>
                <para>
                    <methodname>formNote($name, $value = null)</methodname>: Creates a
                    simple text note. (e.g. as element for headlines in a
                    <classname>Zend_Form</classname> object)
                </para>

<programlisting language="php"><![CDATA[
echo $this->formNote(null, 'This is an example text.');
// Output: This is an example text.
]]></programlisting>
            </listitem>

            <listitem>
                <para>
                    <methodname>formPassword($name, $value, $attribs)</methodname>: Creates an
                    &lt;input type="password" /&gt; element.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>formRadio($name, $value, $attribs, $options, $listsep)</methodname>:
                    Creates a series of &lt;input type="radio" /&gt; 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.
                </para>

<programlisting language="php"><![CDATA[
// 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>
*/
]]></programlisting>
            </listitem>

            <listitem>
                <para>
                    <methodname>formReset($name, $value, $attribs)</methodname>: Creates an
                    &lt;input type="reset" /&gt; element.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>formSelect($name, $value, $attribs, $options)</methodname>:
                    Creates a &lt;select&gt;...&lt;/select&gt; block, with one
                    &lt;option&gt;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.
                </para>

<programlisting language="php"><![CDATA[
// 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>
*/
]]></programlisting>
            </listitem>

            <listitem>
                <para>
                    <methodname>formSubmit($name, $value, $attribs)</methodname>: Creates an
                    &lt;input type="submit" /&gt; element.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>formText($name, $value, $attribs)</methodname>: Creates an
                    &lt;input type="text" /&gt; element.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>formTextarea($name, $value, $attribs)</methodname>: Creates a
                    &lt;textarea&gt;...&lt;/textarea&gt; block.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>url($urlOptions, $name, $reset, $encode)</methodname>: Creates a
                    <acronym>URL</acronym> string based on a named route.
                    <varname>$urlOptions</varname> should be an associative array of key/value pairs
                    used by the particular route.
                </para>

<programlisting language="php"><![CDATA[
// 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
]]></programlisting>
            </listitem>

            <listitem>
                <para>
                    <methodname>serverUrl($requestUri = null)</methodname>: Helper
                    for returning the current server URL (optionally with request URI).
                </para>

<programlisting language="php"><![CDATA[
// 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
]]></programlisting>
            </listitem>

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

        <para>
            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.
        </para>

        <programlisting language="php"><![CDATA[
// 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>
]]></programlisting>

        <para>
            The resulting output from the view script will look something like this:
        </para>

        <programlisting language="php"><![CDATA[
<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>
]]></programlisting>

        <xi:include href="Zend_View-Helpers-Action.xml" />
        <xi:include href="Zend_View-Helpers-BaseUrl.xml" />
        <xi:include href="Zend_View-Helpers-Currency.xml" />
        <xi:include href="Zend_View-Helpers-Cycle.xml" />
        <xi:include href="Zend_View-Helpers-Partial.xml" />
        <xi:include href="Zend_View-Helpers-Placeholder.xml" />
        <xi:include href="Zend_View-Helpers-Doctype.xml" />
        <xi:include href="Zend_View-Helpers-Gravatar.xml" />
        <xi:include href="Zend_View-Helpers-HeadLink.xml" />
        <xi:include href="Zend_View-Helpers-HeadMeta.xml" />
        <xi:include href="Zend_View-Helpers-HeadScript.xml" />
        <xi:include href="Zend_View-Helpers-HeadStyle.xml" />
        <xi:include href="Zend_View-Helpers-HeadTitle.xml" />
        <xi:include href="Zend_View-Helpers-HtmlObject.xml" />
        <xi:include href="Zend_View-Helpers-InlineScript.xml" />
        <xi:include href="Zend_View-Helpers-RenderToPlaceholder.xml" />
        <xi:include href="Zend_View-Helpers-Json.xml" />
        <xi:include href="Zend_View-Helpers-Navigation.xml" />
        <xi:include href="Zend_View-Helpers-Translate.xml" />
        <xi:include href="Zend_View-Helpers-UserAgent.xml" />
    </sect2>

    <sect2 id="zend.view.helpers.paths">
        <title>Helper Paths</title>

        <para>
            As with view scripts, your controller can specify a stack of paths
            for <classname>Zend_View</classname> to search for helper classes. By default,
            <classname>Zend_View</classname> looks in "Zend/View/Helper/*" for helper
            classes. You can tell <classname>Zend_View</classname> to look in other
            locations using the <methodname>setHelperPath()</methodname> and
            <methodname>addHelperPath()</methodname> 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.
        </para>

        <programlisting language="php"><![CDATA[
$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');
]]></programlisting>

        <para>
            In fact, you can "stack" paths using the
            <methodname>addHelperPath()</methodname> method. As you add paths to the stack,
            <classname>Zend_View</classname> 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.
        </para>

        <programlisting language="php"><![CDATA[
$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".
]]></programlisting>
    </sect2>

    <sect2 id="zend.view.helpers.custom">
        <title>Writing Custom Helpers</title>

        <para>
            Writing custom helpers is easy; just follow these rules:
        </para>

        <itemizedlist>
            <listitem>
                <para>
                    While not strictly necessary, we recommend either implementing
                    <classname>Zend_View_Helper_Interface</classname> or extending
                    <classname>Zend_View_Helper_Abstract</classname> when creating your
                    helpers. Introduced in 1.6.0, these simply define a
                    <methodname>setView()</methodname> 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.
                </para>
            </listitem>

            <listitem>
                <para>
                    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 <methodname>addHelperPath()</methodname> or
                    <methodname>setHelperPath()</methodname>).
                </para>
            </listitem>

            <listitem>
                <para>
                    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()".
                </para>
            </listitem>

            <listitem>
                <para>
                    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.
                </para>
            </listitem>

            <listitem>
                <para>
                    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".
                </para>
            </listitem>
        </itemizedlist>

        <para>
            Place the helper class file somewhere in your helper path stack, and
            <classname>Zend_View</classname> will automatically load, instantiate,
            persist, and execute it for you.
        </para>

        <para>
            Here is an example of our <classname>SpecialPurpose</classname> helper code:
        </para>

        <programlisting language="php"><![CDATA[
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);
    }
}
]]></programlisting>

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

        <programlisting language="php"><![CDATA[
// remember, in a view script, $this refers to the Zend_View instance.
echo $this->specialPurpose();
echo $this->specialPurpose();
echo $this->specialPurpose();
]]></programlisting>

        <para>
            The output would look something like this:
        </para>

        <programlisting language="php"><![CDATA[
I have seen 'The Jerk' 1 time(s).
I have seen 'The Jerk' 2 time(s).
I have seen 'The Jerk' 3 time(s).
]]></programlisting>

        <para>
            Sometimes you will need access to the calling <classname>Zend_View</classname>
            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
            <methodname>setView($view)</methodname> method, like the following:
        </para>

        <programlisting language="php"><![CDATA[
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);
    }
}
]]></programlisting>

        <para>
            If your helper class has a <methodname>setView()</methodname> 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.
        </para>

        <para>
            If you are extending <classname>Zend_View_Helper_Abstract</classname>, you do
            not need to define this method, as it is defined for you.
        </para>
    </sect2>

    <sect2 id="zend.view.helpers.registering-concrete">
        <title>Registering Concrete Helpers</title>

        <para>
            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
            <methodname>registerHelper()</methodname> method, which expects two arguments: the
            helper object, and the name by which it will be registered.
        </para>

        <programlisting language="php"><![CDATA[
$helper = new My_Helper_Foo();
// ...do some configuration or dependency injection...

$view->registerHelper($helper, 'foo');
]]></programlisting>

        <para>
            If the helper has a <methodname>setView()</methodname> method, the view object will call
            this and inject itself into the helper on registration.
        </para>

        <note>
            <title>Helper name should match a method</title>

            <para>
                The second argument to <methodname>registerHelper()</methodname> is the name of the
                helper. A corresponding method name should exist in the helper; otherwise,
                <classname>Zend_View</classname> will call a non-existent method when invoking the
                helper, raising a fatal <acronym>PHP</acronym> error.
            </para>
        </note>
    </sect2>
</sect1>
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