PHP邮件收发，和编码问题。数据匹配

<?php
header("content-type:text/html; charset=UTF-8");
/*
 * record kid words and insert into database
 * user by sending email to publication kid words
 *
 */
include 'POP3.php';
include 'email_class.php';
include 'Mail_mimeDecode.php';
//include 'include/compatible.php';
include 'include/extend_common.php';
//include '../../htdocs/include/extend_common.php';
define('POST_from_EMAIL',   1);
define('DATABASE_CONNECTION_ERROR', 2);//数据库连接失败错误
define('EMAIL_CONNECTION_ERROR', 3);//邮箱连接失败错误
define('ACCOUNT_ERROR',    4);//邮箱的账号错误
define('SIGN_EMAIL_ERROR',   5);//邮件标记删除错误
define('DELELET_ERROR',    6);//删除邮件错误
define('INSERT_ERROR',    7);//插入数据失败错误
class mail_data {
 function mail_data(){
  include 'config.php';  
  $mail_log=fopen("mail_log.txt","a+");
  $conn=@mysql_connect($db_host,$db_user,$db_password);
  if($conn){
   mysql_select_db('t',$conn);
   mysql_query("set names utf8");
   $pop3=new Net_POP3();
   //判断连接是否成功
   if ($pop3->connect($host,110)){
    //判断登入是否成功
    if($pop3->login($user,$password)===true){
     $list=$pop3->_cmdList();
     $sum=$pop3->_cmdStat();
     //每次取多少邮件
     $step=2;
     $r=0;
     //先对邮箱取$step邮件
     for($n=0;$n<$sum[0];$n+=$step){
      $t=0;
      $users=array();
      $mail=array();
      $offset=($sum[0]-$n)<$step?