Adds iTunes podcasting tags to a WordPress RSS2 feed for post type "podcast"

wordpress-itunes-feed.php

<?php

/* BEGIN PODCASTING FILTER HOOKS */

function example_add_itunes_namespace(  )
{
    if (get_post_type()==='podcast') {
        echo 'xmlns:itunes="http://www.itunes.com/dtds/podcast-1.0.dtd"';
    }
}

function example_add_itunes_header_tags(  )
{
    if (get_post_type()!=='podcast') {
        return;
    }

    // These could be set up as custom meta
    $subtitle = 'Podcast subtitle goes here.';
    $summary  = 'Podcast summary goes here.';
    $owner    = array(
        'name'  => 'Podcast Owner',
        'email' => '[email protected]',
    );
    $feed_img = 'http://www.example.org/path/to/podcast/image.jpg';

    // DON'T FORGET TO UPDATE THE CATEGORIES BELOW
?>
        <itunes:subtitle><?=$subtitle?></itunes:subtitle>
        <itunes:author><?bloginfo('name')?></itunes:author>
        <itunes:summary><?=$summary?></itunes:summary>
        <itunes:owner>
            <itunes:name><?=$owner['name']?></itunes:name>
            <itunes:email><?=$owner['email']?></itunes:email>
        </itunes:owner>
        <itunes:image
            href="<?=$feed_img?>" />
        <itunes:category text="Category 1">
            <itunes:category text="Subcategory 1" />
        </itunes:category>
        <itunes:category text="Category 2" />
<?php
}

function example_add_itunes_item_tags(  )
{
    if (get_post_type()!=='podcast') {
        return;
    }

    global $post;
    $item_img = 'http://www.example.org/path/to/podcast/image.jpg';

    // Creates a crude excerpt
    $excerpt_array = explode(' ', strip_tags($post->post_content));
    $excerpt = $excerpt_array[0];
    $count = count($excerpt_array);
    $length = min(30, $count);
    for ($i=1; $i<$length; $i++) {
        $excerpt .= ' ' . $excerpt_array[$i];
    }
    $excerpt .= ' ' . preg_replace('/\W$/', '', $excerpt_array[$i]) . '...';
?> 
            <itunes:author><?bloginfo('name')?></itunes:author>
            <itunes:summary><?=$excerpt?></itunes:summary>
            <itunes:image
                href="<?=$item_img?>" />
<?php
}

function example_setup_podcast()
{
    add_action('rss2_ns',   'example_add_itunes_namespace');
    add_action('rss2_head', 'example_add_itunes_header_tags');
    add_action('rss2_item', 'example_add_itunes_item_tags');
}
add_action('after_setup_theme', 'example_setup_podcast');

/* END PODCASTING FILTER HOOKS */