php中判断是gbk还是utf-8

// 返回: true - 含GB编码 false - 为UTF-8编码

function is_gb2312($str)
{
        for($i=0; $i<strlen($str); $i++) {
                $v = ord( $str[$i] );
                if( $v > 127) {
                        if( ($v >= 228) && ($v <= 233) )
                        {
                                if( ($i+2) >= (strlen($str) - 1)) return true;  // not enough characters
                                $v1 = ord( $str[$i+1] );
                                $v2 = ord( $str[$i+2] );
                                if( ($v1 >= 128) && ($v1 <=191) && ($v2 >=128) && ($v2 <= 191) ) // utf编码
                                        return false;
                                else
                                        return true;
                        }
                }
        }
        return true;
}

-----------------------------------------------------------------------------------------------------------------------------------------------------------

判断中文和编码有关 gbk是双字节，utf8是三字节，可以根据 中文的范围来判断    


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

二、代码例子 

   1.  //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));        
 }        
       
 //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);        
 }