function highlight($text) {
  if(isset($_GET['highlight'])) {
    $highlight = explode('+',trim(urlencode($_GET['highlight'])));
    for($i=0;$i < count($highlight);$i++) {
      $text = preg_replace("/".$highlight[$i]."/i","<span class=\"highlighted\">".$highlight[$i]."</span>",$text);
    }
  }
  return $text;
}

function highlight ($text) {
  if (isset ($_GET['highlight'])) {
    $highlight = explode ('+', trim (urlencode ($_GET['highlight'])));
    for ($i = 0; $i < count ($highlight); ++$i) {
      $pattern = sprintf ('/\b%s\b/i', $highlight[$i]);
      $replace = sprintf ('<span class="highlighted">%s</span>', $highlight[$i]);
      $text    = preg_replace($pattern, $replace, $text);
    }
  }
  return $text;
}

$pattern = sprintf ('/\b(%s)\b/i', $highlight[$i]);
$replace = '<span class="highlighted">\\1</span>';