phpdoc: function return type

Tommy <[email protected]>
Newsgroups comp.lang.php
Organization Aioe.org NNTP Server
Message-ID <[email protected]> 
/**
  * @return int|exit
  */
function err($message, $exitCode) {
     $int = fwrite(STDERR, $message);

     if (null !== $exitCode) {
         exit($exitCode);
     }

     return $int;
}

In your opinion, int|exit is good as a type for @return tag?
Or it would be better int|null?
Or it would be better simply int?
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