[Plugin] Flipboard feed modifications

Flipboard-feed.php

<?php
/*
 * Plugin Name:   Flipboard RSS Feed
 * Plugin URI:    http://www.gitnerd.com
 * Description:   A plugin to customize the default RSS Feed according to Flipboard technical specifications.
 * Version:       1.0
 * Author:        oxocode
 * Author URI:    http://www.gitnerd.com
 */
 
 
add_filter( 'the_content_feed', 'flipboard_title_and_subtitle' );
 
function flipboard_title_and_subtitle( $content ) {
    global $post;
    $post_subtitle = get_post_meta( $post->ID, 'subtitle', TRUE );
    // add hgroup only if the Custom Field is set
    if ( $post_subtitle ) {
        $hgroup = '<hgroup><h1>' . $post->post_title . '</h1>';
        $hgroup .= '<h2>' . $post_subtitle . '</h2></hgroup>';
        return $hgroup . $content;
    } else {
        return $content;
    }
}
add_filter( 'the_content_feed', 'flipboard_pull_quotes' );
 
function flipboard_pull_quotes( $content ) {
    // replace blockquote tag with aside
    return str_replace( 'blockquote>', 'aside>', $content );
}
add_filter( 'rss2_item', 'flipboard_attached_images' );
 
function flipboard_attached_images() {
    global $post;
    $attachments = get_posts( array(
        'post_type' => 'attachment',
        'post_mime_type' => 'image',
        'posts_per_page' => -1,
        'post_parent' => $post->ID,
        'exclude' => get_post_thumbnail_id()
    ) );
    if ( $attachments ) {
        foreach ( $attachments as $att ) {
            $img_attr = wp_get_attachment_image_src( $att->ID, 'full' );
            ?>
            <media:content url="<?php echo $img_attr[0]; ?>" type="<?php echo $att->post_mime_type; ?>" medium="image" width="<?php echo $img_attr[1]; ?>" height="<?php echo $img_attr[2]; ?>">
                <media:description type="plain"><![CDATA[<?php echo $att->post_title; ?>]]></media:description>
                <media:copyright><?php echo get_the_author(); ?></media:copyright>
            </media:content>
            <?php
        }
    }
    add_filter( 'rss2_item', 'flipboard_attached_videos' );
 
function flipboard_attached_videos() {
    global $post;
    $attachments = get_posts( array(
        'post_type' => 'attachment',
        'post_mime_type' => 'video',
        'posts_per_page' => -1,
        'post_parent' => $post->ID,
        'exclude' => get_post_thumbnail_id()
    ) );
    if ( $attachments ) {
        foreach ( $attachments as $att ) {
            $video_url = wp_get_attachment_url( $att->ID );
            $parts = explode( '|', $att->post_content );
            ?>
            <media:content url="<?php echo $video_url; ?>" type="<?php echo $att->post_mime_type; ?>">
                <media:description type="plain"><![CDATA[<?php echo $att->post_title; ?>]]></media:description>
                <media:copyright><?php echo get_the_author(); ?></media:copyright>
                <media:thumbnail url="<?php echo $parts[0]; ?>" width="<?php echo $parts[1]; ?>" height="<?php echo $parts[2]; ?>" />
            </media:content>
            <?php
        }
    }
}
add_filter( 'rss2_item', 'flipboard_attached_audio' );
 
function flipboard_attached_audio() {
    global $post; 
    $attachments = get_posts( array(
        'post_type' => 'attachment',
        'post_mime_type' => 'audio',
        'posts_per_page' => -1,
        'post_parent' => $post->ID,
        'exclude' => get_post_thumbnail_id()
    ) );
    if ( $attachments ) {
        foreach ( $attachments as $att ) {
            $audio_url = wp_get_attachment_url( $att->ID );
            $parts = explode( '|', $att->post_content );
            $headers = get_headers( $audio_url, 1 );
            $filesize = $headers['Content-Length'];
            ?>
            <media:content url="<?php echo $audio_url; ?>" fileSize="<?php echo $filesize; ?>" type="<?php echo $att->post_mime_type; ?>">
                <media:description type="plain"><![CDATA[<?php echo $att->post_title; ?>]]></media:description>
                <media:copyright><?php echo get_the_author(); ?></media:copyright>
                <media:thumbnail url="<?php echo $parts[0]; ?>" width="<?php echo $parts[1]; ?>" height="<?php echo $parts[2]; ?>" />
            </media:content>
            <?php
        }
    }
}
add_filter( 'the_content_feed', 'flipboard_slideshow' );
 
function flipboard_slideshow( $content ) {
    global $post;
    $attachments = get_posts( array(
        'post_type' => 'attachment',
        'post_mime_type' => 'image',
        'posts_per_page' => -1,
        'post_parent' => $post->ID,
        'exclude'     => get_post_thumbnail_id()
    ) );
    if ( $attachments ) {
        $slide = '<section class="fl-slideshow"><h1>' . $post->post_title . '</h1>';
        foreach ( $attachments as $att ) {
            $img_attr = wp_get_attachment_image_src( $att->ID, 'full' );
            $slide .= '<figure>
                <img src="' . $img_attr[0] . '" width="' . $img_attr[1] . '" height="' . $img_attr[2] . '">
                <figcaption>' . $att->post_title . '</figcaption>
            </figure>';
        }
        $slide .= '</section>';
        return $content . $slide;
    } else {
        return $content;
    }
}
?>