[WP] post_gallery()

<?php
function post_gallery( $p = 0 ) {

    // globals
    global $post;

    $post_id = ( $p === 0 ) ? $post->ID : $p;

    // vars
    $r = $r_list = $r_imgs = '';
    $i = 0;
    $args = array(
        'post_type' => 'attachment',
        'post_mime_type' => 'image',
        'numberposts' => -1,
        'post_status' => null,
        'post_parent' => $post_id
    );

    // get attachments
    $attachments = get_posts($args);

    // if any
    if ( $attachments ) {

        // loop attachments
        foreach ( $attachments as $img ) {

            // vars
            $img_thumb_atts = wp_get_attachment_image_src( $img->ID, 'small' );
            $img_full_atts = wp_get_attachment_image_src( $img->ID, 'full' );
            $img_desc = $img->post_excerpt;

            // counter
            $i++;

            // html for navigation list
            $r_list .= '<li class="item">';
                $r_list .= '<a href="#" rel="' . $i . '"';
                if ( $i == 1 )
                    $r_list .= ' class="selected"';
                $r_list .= '>';
                    $r_list .= '<img src="' . $img_thumb_atts[0] . '" />';
                $r_list .= '</a>';
            $r_list .= '</li><!-- /.item -->';

            // html for the single image
            $r_imgs .= '<div id="' . $i. '" class="photos_viewbox">';
                $r_imgs .= '<a href="' . $img_full_atts[0] . '" class="single_image" title="">';
                    $r_imgs .= '<img src="' . $img_full_atts[0] . '" alt="" title="" />';
                $r_imgs .= '</a>';
                $r_imgs .= '<a href="javascript:photos.cycleit(\'prev\')" class="photos_prev"> </a>';
                $r_imgs .= '<a href="javascript:photos.cycleit(\'next\')" class="photos_next"> </a>';
                $r_imgs .= '<p class="photos_number">' . sprintf( __( '%1$s / %2$s' ), $i, count($attachments) ) . '</p>';
                $r_imgs .= '<p class="photos_number">' . $img_desc . '</p>';
            $r_imgs .= '</div><!-- /.photos_viewbox -->';
        }

        // concatenate the html
        $r .= '<div id="gallery-slider">';
            $r .= '<div class="photos-next"></div><div class="photos-prev"></div>';
            $r .= '<div class="carousel-gallery">';
                $r .= '<ul id="photos" class="photos_thumb">';
                    $r .= $r_list;
                $r .= '</ul><!-- /#photos -->';
            $r .= '</div><!-- /.carousel-gallery -->';
        $r .= '</div><!-- /#gallery-slider -->';
        $r .= $r_imgs;
        $r .= '<script type="text/javascript">
        var photos=new ddtabcontent("photos")
        photos.setpersist(true)
        photos.setselectedClassTarget("link")
        photos.init()
        </script>';

        // print the result
        return $r;
    }
}