Truncate a HTML formatted text with SMARTY

I've got a variable which is formatted with random HTML code. I call it to {$text} and i truncate it.

The value is for example:

<div>Lorem <i>ipsum <b>dolor <span>sit </span>amet</b>, con</i> elit.</div>

If i truncate the text's first ~30 letters, I'll get this:

<div>Lorem <i>ipsum <b>dolor <span>sit

The problem is, I can't close the elements. So, I need a script, which check the <*> elements in the code (where * could be anything), and if it dont have a close tag, close 'em.

Please help me in this. Thanks.

Solution after hours, and 4 vote-up @ stackoverflow:

PHP:

...
function closetags($content) {
   preg_match_all('#<(?!meta|img|br|hr|input\b)\b([a-z]+)(?: .*)?(?<![/|/ ])>#iU', $content, $result);
    $openedtags = $result[1];
  preg_match_all('#</([a-z]+)>#iU', $content, $result);
 $closedtags = $result[1];
  $len_opened = count($openedtags);
  if (count($closedtags) == $len_opened) {
       return $content;
  }
  $openedtags = array_reverse($openedtags);
  for ($i=0; $i < $len_opened; $i++) {
        if (!in_array($openedtags[$i], $closedtags)) {
         $content .= '</'.$openedtags[$i].'>';
       } else {
           unset($closedtags[array_search($openedtags[$i], $closedtags)]);
        }
  }
  return $content;
}
...

the TPL:

{$pages[j].text|truncate:300|@closetags}

Solution

Pull out all the open tags, push them into an array (array_1) one-by-one.

Pull out all of the closed tags, push them into an array (array_2) one-by-on (this includes self closing tags).

For the tags in the first array (array_1) that are not found in the second array (array_2), add them to the html.

[edit]

Of course, this method fails miserably if you do not write proper html... but whatchagonnado?

Another way would be to look ahead in the string to see which tags are closed and close them as needed.