thinkphp 模板截取中文字符串函数

项目开发中，常常会遇到中文字符串截取问题，例如新闻标题太长需要用“...”代替

//函数解释：
//msubstr($str, $start=0, $length, $charset=”utf-8″, $suffix=true)
//$str:要截取的字符串
// $start=0：开始位置，默认从0开始
// $length：截取长度
// $charset=”utf-8″：字符编码，默认UTF－8
// $suffix=true：是否在截取后的字符后面显示省略号，默认true显示，false为不显示
//模版使用：{$vo.title|msubstr=0,5,'utf-8',false}
//把如下代码粘贴到thinkphp核心包的/common/functions.php 的最后便可在html模型里直接使用

//截取字符串
function msubstr($str, $start=0, $length, $charset="utf-8", $suffix=true)  
{  
	if(function_exists("mb_substr"))
	{  
		if($suffix)  
			return mb_substr($str, $start, $length, $charset)."...";  
		else
			return mb_substr($str, $start, $length, $charset);  
	}  
	elseif(function_exists('iconv_substr')) 
	{  
		if($suffix)  
			return iconv_substr($str,$start,$length,$charset)."...";  
		else
			return iconv_substr($str,$start,$length,$charset);  
	}  
	$re['utf-8']   = "/[x01-x7f]|[xc2-xdf][x80-xbf]|[xe0-xef]
	[x80-xbf]{2}|[xf0-xff][x80-xbf]{3}/";  
	$re['gb2312'] = "/[x01-x7f]|[xb0-xf7][xa0-xfe]/";  
	$re['gbk']    = "/[x01-x7f]|[x81-xfe][x40-xfe]/";  
	$re['big5']   = "/[x01-x7f]|[x81-xfe]([x40-x7e]|xa1-xfe])/";  
	preg_match_all($re[$charset], $str, $match);  
	$slice = join("",array_slice($match[0], $start, $length));  
	if($suffix) return $slice."…";  
	return $slice;
}