Media Edit

I have the meta in the attachment post but cannot get the value in the front end?
Code:

 $prefix = 'sw_';

       // media meta box
        $meta_boxes[] = array(
            'id'       => 'href',
            'title'    => 'Link for Horizontal Gallery',
            'pages'    => array('attachment'),
            'context'  => 'normal',
            'priority' => 'high',

            'fields' => array(            

                array(
                    'name'  => 'URL',
                    'id'    => $prefix . 'link',
                    'type'  => 'url',
                ),

            )
        );

But $links = rwmb_meta( 'sw_link', 'type=url' ); doesnt return any value when I do a var_dump?
That is why I was trying to find that tutorial I thought I had seen before

yeah I have it working the same way (well should be) with get_post_meta and changed to use the rwmb_meta, but I get the same problem using either method, the variable is not echoing

$images = rwmb_meta( 'sw_gallery_image', 'type=image' );
foreach ( $images as $image ) {
$imgID = $image['ID'];
$url = rwmb_meta( 'sw_link', 'type=url', $imgID );
echo "<a href=' . $url . '></a>";

If I do a var_dump($url); I get the metabox value return, but in the link it isnt, any suggestions?

this was my post_meta $url = get_post_meta($imgID, 'sw_link');