Quotes turn into funny characters when submitted in an HTML form

We have a PHP function that tries to clean up the mess with smart quotes. It’s a bit of a mess, since it’s grown a bit organically as cases popped up during prototype development. It may be of some help, though:

function convert_smart_quotes($string) {
    $search = array(chr(0xe2) . chr(0x80) . chr(0x98),
                    chr(0xe2) . chr(0x80) . chr(0x99),
                    chr(0xe2) . chr(0x80) . chr(0x9c),
                    chr(0xe2) . chr(0x80) . chr(0x9d),
                    chr(0xe2) . chr(0x80) . chr(0x93),
                    chr(0xe2) . chr(0x80) . chr(0x94),
                    chr(226) . chr(128) . chr(153),
                    '’','“','â€<9d>','â€"','  ');

     $replace = array("'","'",'"','"',' - ',' - ',"'","'",'"','"',' - ',' ');

    return str_replace($search, $replace, $string);
}