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<sect3 id="zend.view.helpers.initial.headstyle">
    <title>HeadStyle Helper</title>

    <para>
        The <acronym>HTML</acronym> <emphasis>&lt;style&gt;</emphasis> element is used to include
        <acronym>CSS</acronym> stylesheets inline in the <acronym>HTML</acronym>
        <emphasis>&lt;head&gt;</emphasis> element.
    </para>

    <note>
        <title>Use HeadLink to link CSS files</title>

        <para>
            <link linkend="zend.view.helpers.initial.headlink">HeadLink</link>
            should be used to create <emphasis>&lt;link&gt;</emphasis> elements for
            including external stylesheets. <classname>HeadStyle</classname> is used when
            you wish to define your stylesheets inline.
        </para>
    </note>

    <para>
        The <classname>HeadStyle</classname> helper supports the following methods for
        setting and adding stylesheet declarations:
    </para>

    <itemizedlist>
        <listitem>
            <para>
                <command>appendStyle($content, $attributes = array())</command>
            </para>
        </listitem>

        <listitem>
            <para>
                <command>offsetSetStyle($index, $content, $attributes = array())</command>
            </para>
        </listitem>

        <listitem>
            <para>
                <command>prependStyle($content, $attributes = array())</command>
            </para>
        </listitem>

        <listitem>
            <para>
                <command>setStyle($content, $attributes = array())</command>
            </para>
        </listitem>
    </itemizedlist>

    <para>
        In all cases, <varname>$content</varname> is the actual <acronym>CSS</acronym> declarations.
        <varname>$attributes</varname> are any additional attributes you wish to provide to the
        <property>style</property> tag: lang, title, media, or dir are all permissible.
    </para>

    <note>
        <title>Setting Conditional Comments</title>

        <para>
            <classname>HeadStyle</classname> allows you to wrap the style tag in conditional
            comments, which allows you to hide it from specific browsers. To add the conditional
            tags, pass the conditional value as part of the <varname>$attributes</varname> parameter
            in the method calls.
        </para>

        <example id="zend.view.helpers.initial.headstyle.conditional">
            <title>Headstyle With Conditional Comments</title>

            <programlisting language="php"><![CDATA[
// adding scripts
$this->headStyle()->appendStyle($styles, array('conditional' => 'lt IE 7'));
]]></programlisting>
        </example>
    </note>

    <para>
        <classname>HeadStyle</classname> also allows capturing style declarations; this
        can be useful if you want to create the declarations programmatically,
        and then place them elsewhere. The usage for this will be showed in an
        example below.
    </para>

    <para>
        Finally, you can also use the <methodname>headStyle()</methodname> method to
        quickly add declarations elements; the signature for this is
        <methodname>headStyle($content$placement = 'APPEND', $attributes = array())</methodname>.
        <varname>$placement</varname> should be either 'APPEND', 'PREPEND', or 'SET'.
    </para>

    <para>
        <classname>HeadStyle</classname> overrides each of <methodname>append()</methodname>,
        <methodname>offsetSet()</methodname>, <methodname>prepend()</methodname>, and
        <methodname>set()</methodname> to enforce usage of the special methods as listed above.
        Internally, it stores each item as a <property>stdClass</property> token, which it later
        serializes using the <methodname>itemToString()</methodname> method. This allows you
        to perform checks on the items in the stack, and optionally modify these
        items by simply modifying the object returned.
    </para>

    <para>
        The <classname>HeadStyle</classname> helper is a concrete implementation of the
        <link linkend="zend.view.helpers.initial.placeholder">Placeholder
            helper</link>.
    </para>

    <note>
        <title>UTF-8 encoding used by default</title>

        <para>
            By default, Zend Framework uses <acronym>UTF-8</acronym> as its default encoding, and,
            specific to this case, <classname>Zend_View</classname> does as well. Character encoding
            can be set differently on the view object itself using the
            <methodname>setEncoding()</methodname> method (or the <varname>encoding</varname>
            instantiation parameter). However, since <classname>Zend_View_Interface</classname> does
            not define accessors for encoding, it's possible that if you are using a custom view
            implementation with this view helper, you will not have a
            <methodname>getEncoding()</methodname> method, which is what the view helper uses
            internally for determining the character set in which to encode.
        </para>

        <para>
            If you do not want to utilize <acronym>UTF-8</acronym> in such a situation, you will
            need to implement a <methodname>getEncoding()</methodname> method in your custom view
            implementation.
        </para>
    </note>

    <example id="zend.view.helpers.initial.headstyle.basicusage">
        <title>HeadStyle Helper Basic Usage</title>

        <para>
            You may specify a new style tag at any time:
        </para>

        <programlisting language="php"><![CDATA[
// adding styles
$this->headStyle()->appendStyle($styles);
]]></programlisting>

        <para>
            Order is very important with <acronym>CSS</acronym>; you may need to ensure that
            declarations are loaded in a specific order due to the order of the
            cascade; use the various append, prepend, and offsetSet directives
            to aid in this task:
        </para>

        <programlisting language="php"><![CDATA[
// Putting styles in order

// place at a particular offset:
$this->headStyle()->offsetSetStyle(100, $customStyles);

// place at end:
$this->headStyle()->appendStyle($finalStyles);

// place at beginning
$this->headStyle()->prependStyle($firstStyles);
]]></programlisting>

        <para>
            When you're finally ready to output all style declarations in your
            layout script, simply echo the helper:
        </para>

        <programlisting language="php"><![CDATA[
<?php echo $this->headStyle() ?>
]]></programlisting>
    </example>

    <example id="zend.view.helpers.initial.headstyle.capture">
        <title>Capturing Style Declarations Using the HeadStyle Helper</title>

        <para>
            Sometimes you need to generate <acronym>CSS</acronym> style declarations
            programmatically. While you could use string concatenation,
            heredocs, and the like, often it's easier just to do so by creating
            the styles and sprinkling in <acronym>PHP</acronym> tags.
            <classname>HeadStyle</classname> lets you do just that, capturing it to the stack:
        </para>

        <programlisting language="php"><![CDATA[
<?php $this->headStyle()->captureStart() ?>
body {
    background-color: <?php echo $this->bgColor ?>;
}
<?php $this->headStyle()->captureEnd() ?>
]]></programlisting>

        <para>
            The following assumptions are made:
        </para>

        <itemizedlist>
            <listitem>
                <para>
                    The style declarations will be appended to the stack. If you
                    wish for them to replace the stack or be added to the top,
                    you will need to pass 'SET' or 'PREPEND', respectively, as
                    the first argument to <methodname>captureStart()</methodname>.
                </para>
            </listitem>

            <listitem>
                <para>
                    If you wish to specify any additional attributes for the
                    <emphasis>&lt;style&gt;</emphasis> tag, pass them in an array as
                    the second argument to <methodname>captureStart()</methodname>.
                </para>
            </listitem>
        </itemizedlist>
    </example>
</sect3>
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