php清除word 没用的标签，并保留常见标签

function ClearHtml1($content, $allowtags = '<p><span><strong><br/><br><div><ul><li><a><ol><i>')
{
    mb_regex_encoding('UTF-8');
    // replace MS special characters first
    $search = array(
        '/‘/u',
        '/’/u',
        '/“/u',
        '/”/u',
        '/—/u'
    );
    $replace = array(
        '\'',
        '\'',
        '"',
        '"',
        '-'
    );
    $content = preg_replace($search, $replace, $content);
    // make sure _all_ html entities are converted to the plain ascii equivalents - it appears
    // in some MS headers, some html entities are encoded and some aren't
    $content = html_entity_decode($content, ENT_QUOTES, 'UTF-8');
    // try to strip out any C style comments first, since these, embedded in html comments, seem to
    // prevent strip_tags from removing html comments (MS Word introduced combination)
    if (mb_stripos($content, '/*') !== FALSE) {
        $content = mb_eregi_replace('#/\*.*?\*/#s', '', $content, 'm');
    }
    // introduce a space into any arithmetic expressions that could be caught by strip_tags so that they won't be
    // '<1' becomes '< 1'(note: somewhat application specific)
    $content = preg_replace(array(
        '/<([0-9]+)/'
    ), array(
        '< $1'
    ), $content);

    $content = strip_tags($content, $allowtags);
    // eliminate extraneous whitespace from start and end of line, or anywhere there are two or more spaces, convert it to one
    $content = preg_replace(array(
        '/^\s\s+/',
        '/\s\s+$/',
        '/\s\s+/u'
    ), array(
        '',
        '',
        ' '
    ), $content);
    // strip out inline css and simplify style tags
    $search = array(
        '#<(strong|b)[^>]*>(.*?)</(strong|b)>#isu',
        '#<(em|i)[^>]*>(.*?)</(em|i)>#isu',
        '#<u[^>]*>(.*?)</u>#isu'
    );
    $replace = array(
        '<b>$2</b>',
        '<i>$2</i>',
        '<u>$1</u>'
    );
    $content = preg_replace($search, $replace, $content);

    // on some of the ?newer MS Word exports, where you get conditionals of the form 'if gte mso 9', etc., it appears
    // that whatever is in one of the html comments prevents strip_tags from eradicating the html comment that contains
    // some MS Style Definitions - this last bit gets rid of any leftover comments */
    $num_matches = preg_match_all("/\<!--/u", $content, $matches);
    if ($num_matches) {
        $content = preg_replace('/\<!--(.)*--\>/isu', '', $content);
    }
    return $content;
}