php字符串读取函数

function cc_msubstr($str, $length, $start=0, $charset="utf-8", $suffix=true){
if(function_exists("mb_substr")){
return mb_substr($str, $start, $length, $charset);
}elseif(function_exists('iconv_substr')){
return iconv_substr($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;
}