thinkphp截取文字部分字符串

ThinkPHP有一个内置字符截取函数msubstr()如下：

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 

在function.php定义msubstr函数

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."...";
    }else{
        return $slice;
    }
}

调用该函数：

{$vo['title']|msubstr=5,5,'utf-8',false}