filtre couper en gardant mise en page

/*
 * Coupe une chaine en gardant le formatage HTML
 * @param string $text Texte à couper
 * @param integer $length Longueur à garder
 * @param string $ending Caractères à ajouter à la fin
 * @param boolean $exact Coupure exacte
 * @return string
 */
function couper_html($text, $length, $ending = '...', $exact = false) {
    if(strlen(preg_replace('/<.*?>/', '', $text)) <= $length) {
        return $text;
    }
    preg_match_all('/(<.+?>)?([^<>]*)/is', $text, $matches, PREG_SET_ORDER);
    $total_length = 0;
    $arr_elements = array();
    $truncate = '';
    foreach($matches as $element) {
        if(!empty($element[1])) {
            if(preg_match('/^<\s*.+?\/\s*>$/s', $element[1])) {
            } else if(preg_match('/^<\s*\/([^\s]+?)\s*>$/s', $element[1], $element2)) {
                $pos = array_search($element2[1], $arr_elements);
                if($pos !== false) {
                    unset($arr_elements[$pos]);
                }
            } else if(preg_match('/^<\s*([^\s>!]+).*?>$/s', $element[1], $element2)) {
                array_unshift($arr_elements,
                strtolower($element2[1]));
            }
            $truncate .= $element[1];
        }
        $content_length = strlen(preg_replace('/(&[a-z]{1,6};|&#[0-9]+;)/i', ' ', $element[2]));
        if($total_length >= $length) {
            break;
        } elseif ($total_length+$content_length > $length) {
            $left = $total_length>$length?$total_length-$length:$length-$total_length;
            $entities_length = 0;
            if(preg_match_all('/&[a-z]{1,6};|&#[0-9]+;/i', $element[2], $element3, PREG_OFFSET_CAPTURE)) {
                foreach($element3[0] as $entity) {
                    if($entity[1]+1-$entities_length <= $left) {
                        $left--;
                        $entities_length += strlen($entity[0]);
                    } else break;
                }
            }
            $truncate .= substr($element[2], 0, $left+$entities_length);
            break;
        } else {
            $truncate .= $element[2];
            $total_length += $content_length;
        }
    }
    if(!$exact) {
        $spacepos = strrpos($truncate, ' ');
        if(isset($spacepos)) {
            $truncate = substr($truncate, 0, $spacepos);
        }
    }
    $truncate .= $ending;
    foreach($arr_elements as $element) {
        $truncate .= '</' . $element . '>';
    }
    return $truncate;
}