PHP 문자열 차단(substr의 적용 및 확장)

<?
$a="12me46";
echo(substr($a,2,2));//输出me
?> 

<?php
//中文字符串截取
//http://bbs.it-home.org
function msubstr($str,$start=0,$length,$charset="utf-8",$suffix=true)
{
switch($charset){
 case 'utf-8':$char_len=3;break;
 case 'UTF8':$char_len=3;break;
 default:$char_len=2;
}
//小于指定长度，直接返回
if(strlen($str)<=($length*$char_len)){ 
   return $str;
}
if(function_exists("mb_substr")){   
   $slice= mb_substr($str, $start, $length, $charset);
}else if(function_exists('iconv_substr')){
   $slice=iconv_substr($str,$start,$length,$charset);
}else{ 
   $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;
}
?>