function str_html_encode($str) {
$tags = array("i", "em", "b", "strong", "sup", "strike");
$pattern = '%(?:<|<|\\[)(\\/?(?:' . implode('|', $tags) . '))(?:>|>|\\])%';
$str = htmlentities($str);
$str = preg_replace($pattern, '<$1>', $str);
return $str;
}
