一个很好的中文截取字符窜函数

function cut_str($string,$sublen,$filter=true,$start=0,$code='UTF-8'){
	if($filter) $string=Html2Text($string);
	if($code=='UTF-8'){
		$pa="/[\x01-\x7f]|[\xc2-\xdf][\x80-\xbf]|[\xe0-\xef][\x80-\xbf]{2}|[\xf0-\xff][\x80-\xbf]{3}/";
		preg_match_all($pa,$string,$t_string);
		if(count($t_string[0])-$start>$sublen) return join('',array_slice($t_string[0],$start,$sublen))."...";
		return join('',array_slice($t_string[0],$start,$sublen));
	}else{
		$start=$start*2;
		$sublen=$sublen*2;
		$strlen=strlen($string);
		$tmpstr='';
		for($i=0;$i<$strlen;$i++){
			if($i>=$start&&$i<($start+$sublen)){
				if(ord(substr($string,$i,1))>129){
					$tmpstr.=substr($string,$i,2);
				}else{
					$tmpstr.=substr($string,$i,1);
				}
			}
			if(ord(substr($string,$i,1))>129) $i++;
		}
		if(strlen($tmpstr)<$strlen ) $tmpstr.="...";
		return $tmpstr;
	}
}
function Html2Text($str){
	$str = preg_replace("/<sty(.*)\\/style>|<scr(.*)\\/script>|<!--(.*)-->/isU","",$str);
	$alltext = "";
	$start = 1;
	for($i=0;$i<strlen($str);$i++){
		if($start==0 && $str[$i]==">"){
			$start = 1;
		}else if($start==1){
			if($str[$i]=="<"){
				$start = 0;
				$alltext .= " ";
			}else if(ord($str[$i])>31){
				$alltext .= $str[$i];
			}
		}
	}
	$alltext = str_replace("　"," ",$alltext);
	$alltext = preg_replace("/&([^;&]*)(;|&)/","",$alltext);
	$alltext = preg_replace("/[ ]+/s"," ",$alltext);
	return $alltext;
}