1. 截取GB2312中文字符串

< ?php  
 //截取中文字符串 
 function mysubstr($str, $start, $len) { 
     $tmpstr = ""; 
     $strlen = $start + $len; 
     for($i = 0; $i < $strlen; $i++) { 
         if(ord(substr($str, $i, 1)) > 0xa0) { 
             $tmpstr .= substr($str, $i, 2); 
             $i++; 
         } else 
             $tmpstr .= substr($str, $i, 1); 
     } 
     return $tmpstr; 
 } 
 ?> 
2. 截取utf8编码的多字节字符串

< ?php 
 //截取utf8字符串 
 function utf8Substr($str, $from, $len) 
 { 
     return preg_replace('#^(?:[\x00-\x7F]|[\xC0-\xFF][\x80-\xBF]+){0,'.$from.'}'. 
                        '((?:[\x00-\x7F]|[\xC0-\xFF][\x80-\xBF]+){0,'.$len.'}).*#s', 
                        '$1',$str); 
 } 
 ?> 
3. UTF-8、GB2312都支持的汉字截取函数
< ?php 
 /*  
 Utf-8、gb2312都支持的汉字截取函数  
 cut_str(字符串, 截取长度, 开始长度, 编码);  
 编码默认为 utf-8  
 开始长度默认为 0  
 */  
   
 function cut_str($string, $sublen, $start = 0, $code = 'UTF-8')  
 {  
     if($code == 'UTF-8')  
     {  
         $pa = "/[\x01-\x7f]|[\xc2-\xdf][\x80-\xbf]|\xe0[\xa0-\xbf][\x80-\xbf]|[\xe1-\xef][\x80-\xbf][\x80-\xbf]|\xf0[\x90-\xbf][\x80-\xbf][\x80-\xbf]|[\xf1-\xf7][\x80-\xbf][\x80-\xbf][\x80-\xbf]/";  
         preg_match_all($pa, $string, $t_string);  
   
         if(count($t_string[0]) - $start > $sublen) return join('', array_slice($t_string[0], $start, $sublen))."...";  
         return join('', array_slice($t_string[0], $start, $sublen));  
     }  
     else  
     {  
         $start = $start*2;  
         $sublen = $sublen*2;  
         $strlen = strlen($string);  
         $tmpstr = '';  
   
         for($i=0; $i< $strlen; $i++)  
         {  
             if($i>=$start && $i< ($start+$sublen))  
             {  
                 if(ord(substr($string, $i, 1))>129)  
                 {  
                     $tmpstr.= substr($string, $i, 2);  
                 }  
                 else  
                 {  
                     $tmpstr.= substr($string, $i, 1);  
                 }  
             }  
             if(ord(substr($string, $i, 1))>129) $i++;  
         }  
         if(strlen($tmpstr)< $strlen ) $tmpstr.= "...";  
         return $tmpstr;  
     }  
 }  
   
 $str = "abcd需要截取的字符串";  
 echo cut_str($str, 8, 0, 'gb2312');  
 ?> 
4. BugFree 的字符截取函数
< ?php  
 /**  
  * @package     BugFree  
  * @version     $Id: FunctionsMain.inc.php,v 1.32 2005/09/24 11:38:37 wwccss Exp $  
  *  
  *  
  * Return part of a string(Enhance the function substr())  
  *  
  * @author                   Chunsheng Wang <wwccss@263.net>  
  * @param string  $String  the string to cut.  
  * @param int     $Length  the length of returned string.  
  * @param booble  $Append  whether append "...": false|true  
  * @return  string           the cutted string.  
  */  
 function sysSubStr($String,$Length,$Append = false)  
 {  
     if (strlen($String) < = $Length )  
     {  
         return $String;  
     }  
     else  
     {  
         $I = 0;  
         while ($I < $Length)  
         {  
             $StringTMP = substr($String,$I,1);  
             if ( ord($StringTMP) >=224 )  
             {  
                 $StringTMP = substr($String,$I,3);  
                 $I = $I + 3;  
             }  
             elseif( ord($StringTMP) >=192 )  
             {  
                 $StringTMP = substr($String,$I,2);  
                 $I = $I + 2;  
             }  
             else  
             {  
                 $I = $I + 1;  
             }  
             $StringLast[] = $StringTMP;  
         }  
         $StringLast = implode("",$StringLast);  
         if($Append)  
         {  
             $StringLast .= "...";  
         }  
         return $StringLast;  
     }  
 }  
   
 $String = "CodeBit.cn -- 简单、精彩、通用";  
 $Length = "18";  
 $Append = false;  
 echo sysSubStr($String,$Length,$Append);  
 ?>