正则匹配 只保留中文 英文 数字

function match_chinese($chars,$encoding='utf8'){$pattern =($encoding=='utf8')?'/[\x{4e00}-\x{9fa5}a-zA-Z0-9]/u':'/[\x80-\xFF]/';preg_match_all($pattern,$chars,$result);$temp =join('',$result[0]);return $temp;}