/**
  * Update the meta value for the single view checkbox.
  *
  * @param  integer $post_id  The post ID being passed on save.
  *
  * @return void
  */
 function save_checkbox($post_id)
 {
     // Do our nonce comparison.
     if (empty($_POST['svo_meta_nonce']) || !wp_verify_nonce(sanitize_key($_POST['svo_meta_nonce']), 'svo_meta_nonce')) {
         return;
     }
     // Run various checks to make sure we aren't doing anything weird.
     if (false === RKV_SVO_Helper::meta_save_check($post_id)) {
         return;
     }
     // Check against the post types we've allowed.
     if (!in_array(get_post_type($post_id), RKV_SVO_Helper::get_post_types())) {
         return;
     }
     // Check for the true value being posted.
     if (!empty($_POST['svo-active'])) {
         update_post_meta($post_id, '_svo_active', sanitize_key($_POST['svo-active']));
     } else {
         delete_post_meta($post_id, '_svo_active');
     }
 }