ECPT list by surname

// Add list of attorneys surname first
function display_surname_forname() {
    $args = array( 'post_type' => 'attorneys', 'order'=> 'ASC', 'posts_per_page' => -1 );
    $posts = new WP_query( $args );
//  echo '<pre>',print_r( $posts ),'</pre>';
    if ( $posts->have_posts() ) {   // Loop
        $output = '<ul>';
        while( $posts->have_posts() ) : $posts->the_post();
            $output .= '<li><a href="' . get_permalink() . '" title="' . __( 'View profile for' ) . ': ' . get_the_title() . '">' . get_post_meta( $posts->ID, 'ecpt_surname', true ) . ', ' . get_post_meta( $posts->ID, 'ecpt_forename', true ) . '</a></li>';

        endwhile;   // End Loop

        $output .= '</ul>';

        return $output;

        wp_reset_postdata();

    }

}
add_shortcode( 'attorney-list', 'display_surname_forname' );