PHP选择选项$行发布到电子邮件

Question

我有一个带有选择选项的表单，并且正在尝试将选项$ row [email]发布到电子邮件中，似乎什么也无法工作。我已经搜索了几个小时，似乎什么也没做。任何帮助将不胜感激。 这是表格create-mail.php

        <form action="add-mail.php" method="post">
          <div class="box box-primary">
            <div class="box-header with-border">
              <h3 class="box-title">Compose New Message</h3>
            </div>
            <div class="box-body">
              <div class="form-group">
                <select id="to" name="to" class="form-control">
                  <?php 
                $sql = "SELECT * FROM apply_job_post INNER JOIN users ON apply_job_post.id_user=users.id_user WHERE apply_job_post.id_company='$_SESSION[id_company]' AND apply_job_post.status='2'";
                $result = $conn->query($sql);
                if($result->num_rows > 0) {
                  while($row = $result->fetch_assoc()) {
                    echo '<option value="'.$row['id_user'].'">'.$row['email'].' '.$row['firstname'].' '.$row['lastname'].'</option>';
                  }
                }
                ?>
                </select>
              </div>
              <div class="form-group">
                <input class="form-control" name="subject" placeholder="Subject:">
                <input type="hidden" name="user_email" id="user_email" value="<?php echo $_post['to'];?>" />
                <input type="hidden" name="co_name" id="login_user" value="<?php echo $_SESSION['name'];?>" />
              </div>
              <div class="form-group">
                <textarea class="form-control input-lg" id="description" name="description" placeholder="Job Description"></textarea>
              </div>
            </div>
            <div class="box-footer">
              <div class="pull-right">
                <button type="submit" name="create_mail" class="btn btn-primary"><i class="fa fa-envelope-o"></i> Send</button>
              </div>
              <a href="mailbox.php" class="btn btn-default"><i class="fa fa-times"></i> Discard</a> </div>
          </div>
        </form>

这是add-mail.php

<?php
session_start();

if(empty($_SESSION['id_company'])) {
header("Location: ../index.php");
exit();
}

require_once("../db.php");

if(isset($_POST['create_mail']))
{
         $to  = mysqli_real_escape_string($conn, $_POST['to']);
         $subject = mysqli_real_escape_string($conn, $_POST['subject']);

         $message = "You have a message from"." ". $_POST['co_name'] ."\r\n"; 
         $message .= "Message:"." ". $_POST['description'];

         $headers[] = 'MIME-VERSION: 1.0';
         $headers[] = 'Content-type: text/html; charset=iso-8859-1';
         $headers[] = 'To: '.$to;
         $headers[] = 'From: me@mycompany.com';

         $result = mail($to, $subject, $message, implode("\r\n", $headers)); 

}
?>