一、编码范围
1. GBK (GB2312/GB18030)
\x00-\xff GBK双字节编码范围
\x20-\x7f ASCII
\xa1-\xff 中文
\x80-\xff 中文

2. UTF-8 (Unicode)
\u4e00-\u9fa5 (中文)
\x3130-\x318F (韩文
\xAC00-\xD7A3 (韩文)
\u0800-\u4e00 (日文)
ps: 韩文是大于[\u9fa5]的字符

正则例子:

PLAIN TEXT
PHP:
preg_replace("/([\x80-\xff])/","",$str);
preg_replace("/([u4e00-u9fa5])/","",$str);

二、代码例子

PLAIN TEXT
PHP:
//判断内容里有没有中文-GBK (PHP)
function check_is_chinese($s){
return preg_match('/[\x80-\xff]./', $s);
}
 
//获取字符串长度-GBK (PHP)
function gb_strlen($str){
$count = 0;
for($i=0; $i<strlen($str); $i++){
$s = substr($str, $i, 1);
if (preg_match("/[\x80-\xff]/", $s)) ++$i;
++$count;
}
return $count;
}
 
//截取字符串字串-GBK (PHP)
function gb_substr($str, $len){
$count = 0;
for($i=0; $i<strlen($str); $i++){
if($count == $len) break;
if(preg_match("/[\x80-\xff]/", substr($str, $i, 1))) ++$i;
++$count;
}
return substr($str, 0, $i);
}
 
//统计字符串长度-UTF8 (PHP)
function utf8_strlen($str) {
$count = 0;
for($i = 0; $i <strlen($str); $i++){
$value = ord($str[$i]);
if($value> 127) {
$count++;
if($value>= 192 && $value <= 223) $i++;
elseif($value>= 224 && $value <= 239) $i = $i + 2;

elseif($value>= 240 && $value <= 247) $i = $i + 3;
else die('Not a UTF-8 compatible string');
}
$count++;
}
return $count;
}
 
 
//截取字符串-UTF8(PHP)
function utf8_substr($str,$position,$length){
$start_position = strlen($str);
$start_byte = 0;
$end_position = strlen($str);
$count = 0;
for($i = 0; $i <strlen($str); $i++){
if($count>= $position && $start_position> $i){
$start_position = $i;
$start_byte = $count;
}
if(($count-$start_byte)>=$length) {
$end_position = $i;
break;
}
$value = ord($str[$i]);
if($value> 127){
$count++;
if($value>= 192 && $value <= 223) $i++;
elseif($value>= 224 && $value <= 239) $i = $i + 2;
elseif($value>= 240 && $value <= 247) $i = $i + 3;
else die('Not a UTF-8 compatible string');
}
$count++;
 
}
return(substr($str,$start_position,$end_position-$start_position));
}
 
 
//字符串长度统计-UTF8 [中文3个字节，俄文、韩文占2个字节，字母占1个字节] (Ruby)
def utf8_string_length(str)
temp = CGI::unescape(str)
i = 0;
j = 0;
temp.length.times{|t|
if temp[t] <127
i += 1
elseif temp[t]>= 127 and temp[t] <224
j += 1
if 0 == (j % 2)
i += 2
j = 0
end
else
j += 1
if 0 == (j % 3)
i +=2
j = 0
end
end
}
return i
}
 
//判断是否是有韩文-UTF-8 (javascript)
function checkKoreaChar(str) {
for(i=0; i<str.length; i++) {
if(((str.charCodeAt(i)> 0x3130 && str.charCodeAt(i) <0x318F) || (str.charCodeAt(i)>= 0xAC00 && str.charCodeAt(i) <= 0xD7A3))) {
return true;
}
}
return false;
}
//判断是否有中文字符-GBK (javascript)
function check_chinese_char(s){
return (s.length != s.replace(/[^\x00-\xff]/g,"**").length);
}