Custom strip_word_html

With most web based user input of more than a line of text, it seems I get 90% 'paste from Word'. I've developed this fn over time to try to strip all of this cruft out. A few things I do here are application specific, but if it helps you - great, if you can improve on it or have a better way - please - post it...

<?php

function strip_word_html($text, $allowed_tags = '<b><i><sup><sub><em><strong><u><br>')
{
mb_regex_encoding('UTF-8');
//replace MS special characters first
$search = array('/&lsquo;/u', '/&rsquo;/u', '/&ldquo;/u', '/&rdquo;/u', '/&mdash;/u');
$replace = array('\'', '\'', '"', '"', '-');
$text = preg_replace($search, $replace, $text);
//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
$text = html_entity_decode($text, 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($text, '/*') !== FALSE){
$text = mb_eregi_replace('#/\*.*?\*/#s', '', $text, '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)
$text = preg_replace(array('/<([0-9]+)/'), array('< $1'), $text);
$text = strip_tags($text, $allowed_tags);
//eliminate extraneous whitespace from start and end of line, or anywhere there are two or more spaces, convert it to one
$text = preg_replace(array('/^\s\s+/', '/\s\s+$/', '/\s\s+/u'), array('', '', ' '), $text);
//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>');
$text = preg_replace($search, $replace, $text);
//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", $text, $matches);
if($num_matches){
$text = preg_replace('/\<!--(.)*--\>/isu', '', $text);
}
return $text;
}