如何解决php doc 乱码问题

$file_size = filesize($logName);
 ob_end_clean();
 header("Content-type:application/octet-stream");
 header("Accept-Ranges:bytes");
 header("Accept-Length:$file_size");
 header("Content-Disposition:attachment;filename=" . $fileName);
 $fp = fopen($logName, "r");
 $buffer_size = 1024;
 $cur_pos = 0;
 while (!feof($fp) && $file_size - $cur_pos > $buffer_size) {
 $buffer = fread($fp, $buffer_size);
 echo$buffer;
 $cur_pos+=$buffer_size;
 }
 $buffer = fread($fp, $file_size - $cur_pos);
 echo$buffer;
 fclose($fp);
 return true;