Including or requiring a file that looks like this:

<?
  if (defined('MY_INCLUDE_FILE')) { 
    return;
  }
  define('MY_INCLUDE_FILE', 1);

  ...
?>

causes a parser error on the last line of the main script if this file is included more than once.  The parser error can be silenced by adding one } to the end of the main script for each time that "return" executes.

For example, if that file is included 3 times, }} must be added to the end of the script.