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<sect2 id="zend.filter.set.alpha">
    <title>Alpha</title>

    <para>
        <classname>Zend_Filter_Alpha</classname> is a filter which returns the string
        <varname>$value</varname>, removing all but alphabetic characters. This filter includes an
        option to also allow white space characters.
    </para>

    <sect3 id="zend.filter.set.alpha.options">
        <title>Supported options for Zend_Filter_Alpha</title>

        <para>
            The following options are supported for <classname>Zend_Filter_Alpha</classname>:
        </para>

        <itemizedlist>
            <listitem>
                <para>
                    <emphasis><property>allowwhitespace</property></emphasis>: If this option is
                    set then whitespace characters are allowed. Otherwise they are suppressed. By
                    default whitespace characters are not allowed.
                </para>
            </listitem>
        </itemizedlist>
    </sect3>

    <sect3 id="zend.filter.set.alpha.basic">
        <title>Basic usage</title>

        <para>
            A basic example of usage is below:
        </para>

        <programlisting language="php"><![CDATA[
$filter = new Zend_Filter_Alpha();

print $filter->filter('This is (my) content: 123');
]]></programlisting>

        <para>
            The above example returns 'Thisismycontent'. Notice that the whitespace characters and
            brackets are removed.
        </para>

        <note>
            <para>
                <classname>Zend_Filter_Alpha</classname> works on most languages; however, there
                are three exceptions: Chinese, Japanese and Korean. With these languages the
                english alphabet is used. The language is detected through the use of
                <classname>Zend_Locale</classname>.
            </para>
        </note>
    </sect3>

     <sect3 id="zend.filter.set.alpha.whitespace">
         <title>Allow whitespace characters</title>

        <para>
            <classname>Zend_Filter_Alpha</classname> can also allow whitespace characters. This can
            be useful when you want to strip special characters from a string. See the following
            example:
        </para>

        <programlisting language="php"><![CDATA[
$filter = new Zend_Filter_Alpha(array('allowwhitespace' => true));

print $filter->filter('This is (my) content: 123');
]]></programlisting>

        <para>
            The above example returns 'This is my content '. Notice that the parenthesis, colon, and
            numbers have all been removed while the whitespace characters remain.
        </para>

        <para>
            To change <property>allowWhiteSpace</property> after instantiation the method
            <methodname>setAllowWhiteSpace()</methodname> may be used.
        </para>

        <para>
            To query the current value of <property>allowWhiteSpace</property> the method
            <methodname>getAllowWhiteSpace()</methodname> may be used.
        </para>
    </sect3>
</sect2>
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