gistfile1.txt

  function number_expeditions( $post_ID ) {
    global $wpdb;
    
    if ( !wp_is_post_revision( $post_ID ) ) {
      
      $dispatchNumber = false;
      
      $parent = wp_get_post_parent_id( $post_ID );
      
      $dispatchArgs = array(
        'numberposts' => -1,
        'order' => 'ASC',
        'orderby' => 'date',
        'post_parent' => $parent,
        'post_status' => 'publish',
        'post_type' => 'nse_expedition',
      );
      
      $dispatches = get_children( $dispatchArgs );
      
      if ( !array_key_exists( $post_ID , $dispatches ) ) :
        
        $dispatchNumber = count( $dispatches ) + 1;
        
      else:
        
        $i = 1;
        foreach ( $dispatches as $c => $dispatch ) :
          
          if ( $c == $post_ID ) :
            $dispatchNumber = $i;
          endif;
        
          $i++;
        endforeach;
      
      endif;
      
      if ( $dispatchNumber )
        add_post_meta($post_ID, 'nse_dispatch_number', $dispatchNumber, true);
    }
  }