PHP截取字符串

< ?php 
/* 
Utf-8、gb2312都支持的漢字截取函數 
cut_str(字符串, 截取長度, 開始長度, 編碼); 
編碼默認爲 utf-8 
開始長度默認爲 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'); 
?>

 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編碼的多字節字符串

<?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都支持的漢字截取函數