wp_get_archives doesn't work as array

wp_get_archives works unless I try to output it to an array. If I do that I get this error:

Warning: Invalid argument supplied for foreach() in /home/dotswoof/public_html/beta/wp-content/themes/swoof/archive.php on line 92

Here is the link:
http://www.dotswoof.com/beta/?page_id=68

Here is the code:

$args = array(
                    'type'            => 'postbypost',
                    'format'          => 'link',
                    'show_post_count' => false,
                    'echo'            => 0 );

                    $archive = wp_get_archives($args);

                    foreach ($archive as $post)
                    {
                        echo $post->post_name;
                    }

I don’t know why this isn’t working and I’m on a deadline. Any help would be greatly appreciated.