Multi fields custom metabox

add_action('add_meta_boxes', 'mycpt_meta_boxes');

function mycpt_meta_boxes()
{
    add_meta_box( 'cpt_metabox-1', __( 'Extra fields' ), 'mycpt_meta_box_content', 'post', 'normal', 'high');
}

// }}}
// {{{

function mycpt_meta_box_content()
{
    global $post;

    include 'form.php';
    wp_nonce_field('mycpt_save', 'mycpt_nonce');
}

add_action('save_post', 'mycpt_save_postdata', 10, 2);

function mycpt_save_postdata( $post_id )
{
    global $wpdb;

    if ( !wp_verify_nonce( $_POST['mycpt_nonce'], 'mycpt_save' ) ) {
        return $post_id;
    }

    if ( defined('DOING_AUTOSAVE') && DOING_AUTOSAVE ) {
        return $post_id;
    }

    // Check permissions ....

    /*
     * Videos names/titles
     */
    $videos_titulos = $_POST['video_title'];

    // First is empty
    array_shift($videos_titulos);

    /*
     * Video URLs
     */
    $videos_urls  = $_POST['video_url'];
    // first is empty
    array_shift($videos_urls);

    // How many ?
    $videos_count = sizeof($videos_titulos);
    $videos = array();
    $content = '';

    for ($i = 0; $i <= $videos_count; $i++) {
        $title = $videos_titulos[$i];
        $url    = $videos_urls[$i];

        // check if empty
        if (!empty($title) && !empty($url)) {
            $videos[] = array(
                'title' => $title,
                'url'   => $url,
                'image' => get_youtube_video_thumb($url)
            );
        }
    }

    // Serializamos videos en caso que existan, si no, eliminar el post meta
    if ( sizeof($videos) > 0 ) {
        $content = serialize($videos);
    }


    update_post_meta($post_id, 'videos', $content);
}

/**
 *
 *
 */
function get_youtube_video_thumb($video_url)
{
    $thumb = '';
    $myurl = parse_url($video_url);

    parse_str($myurl['query'], $myquery);

    $video = trim($myquery['v']);

    if ( !empty($video) && strlen($video) > 3 ) {
        $thumb = 'http://img.youtube.com/vi/' . $video . '/default.jpg';
    }

    return $thumb;
}