custom placeholder function

// function to create #_CUSTEVENTPRICE
function my_em_ticket_price($replace, $EM_Event, $result) {
  if ( $result == '#_CUSTEVENTPRICE' ) {
        global $EM_Event;
        $is_open = $EM_Event->get_bookings()->is_open(); // whether there are any available tickets right now
    if ( $is_open ) { // if bookings are enabled and available
        $ticketprice = do_shortcode('[event id="'.$EM_Event->event_id.'"]#_EVENTPRICEMIN[/event]');
    } else { // if bookings are enabled but not available
            global $post;
            $ticketprice = get_post_meta($post->ID, 'Registration fee', true); // get value from custom attribute
    }
    $replace = $ticketprice;
  }
  return $replace;
}
add_filter('em_event_output_placeholder','my_em_ticket_price', 1, 4);