PHP截取中文字符串函数~包括GB2312和UT-8

/* 
utf-8、gb2312都支持的汉字截取函数 
cut_str(字符串, 截取长度, 开始长度, 编码); 
编码默认为 utf-8 
开始长度默认为 0 
*/  
  
function cut_str($string, $sublen, $start = 0, $code = 'utf-8')  
{  
    if($code == 'utf-8')  
    {  
        $pa = "/[\x01-\x7f]|[\xc2-\xdf][\x80-\xbf]|\xe0[\xa0-\xbf][\x80-\xbf]|[\xe1-\xef][\x80-\xbf][\x80-\xbf]|\xf0[\x90-\xbf][\x80-\xbf][\x80-\xbf]|[\xf1-\xf7][\x80-\xbf][\x80-\xbf][\x80-\xbf]/";  
        preg_match_all($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; $i        {  
            if($i>=$start && $i            {  
                if(ord(substr($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)        return $tmpstr;  
    }  
}  
  
$str = "abcd需要截取的字符串";  
echo cut_str($str, 8, 0, 'gb2312');  
?>  


    //截取中文字符串  
   //支持gb2312 
    function mysubstr($str, $start, $len) {  
        $tmpstr = "";  
        $strlen = $start + $len;  
        for($i = 0; $i             if(ord(substr($str, $i, 1)) > 0xa0) {  
                $tmpstr .= substr($str, $i, 2);  
                $i++;  
            } else  
                $tmpstr .= substr($str, $i, 1);  
        }  
        return $tmpstr;  
    }  
?>  



//截取utf8字符串  
function utf8substr($str, $from, $len)  
{  
    return preg_replace('#^(?:[\x00-\x7f]|[\xc0-\xff][\x80-\xbf]+){0,'.$from.'}'.  
                       '((?:[\x00-\x7f]|[\xc0-\xff][\x80-\xbf]+){0,'.$len.'}).*#s',  
                       '$1',$str);  
}  
?>