PHP中GBK和UTF8编码处理（中文，韩文）

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教程: 韩文是大于[u9fa5]的字符

正则例子:
preg_replace("/([x80-xff])/","",$str);
preg_replace("/([u4e00-u9fa5])/","",$str);

二、代码例子

//判断内容里有没有中文-gbk (php教程)
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
}

//判断是否是含有韩文-utf-8 (网页特效)
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);
}