查询不插入

Question

我在页面上有一个代码（insertrespondent2.php），它应该从另一个站点上的表单中插入一些值（registerrespondent2.php）。将值插入数据库后，应显示一个文本，确认已插入值。问题是我确实得到了确认文本，但没有插入任何值。

registerrespondent2.php

<?php
    $quest = "SELECT coalesce(max(rid)+1,1) AS id FROM temp_members_db";
    $result = $mysqli->query($quest);

   if ($result->num_rows > 0) {
     while($row = $result->fetch_array()) {   
   ?>                              
<form action='insertrespondent2.php' method='POST' enctype='multipart/form-data' name='insertrespondent' onsubmit='return validateForm()'>
    <input type='hidden' name='ridsend' value='". $row["id"] ."'>
    <b>Company E-mail:</b><br> <input type='text' size='35' name='minemail'/><br>
    <b>Subject: </b><br><input type='text' size='35' name='subject'/><br>
    <b>First name: </b><br><input type='text' size='35' name='firstname' id='firstname'><br>
    <b>Last name: </b><br><input type='text' size='35' name='lastname' id='lastname'><br>
    <b>Respondent E-mail: </b><br><input type='text' size='35' name='email' id='email'><br><br>
    <b>Message: </b><br><textarea rows='10' cols='30' name='message'></textarea> <br>
    <input type='submit' name='submit' value='Skicka test'>
</form>
<?php  
     }
         } 
 ?>

insertrespondent2.php

$confirm_code=md5(uniqid(rand()));
$firstname = $_POST['firstname'];
$lastname =  $_POST['lastname'];
$email =     $_POST['email'];
$from =      $_POST['minemail'];
$subject =   $_POST['subject'];
$message =   $_POST['message'];
$ridret = $_POST['ridsend'];

$sql= "INSERT INTO temp_members_db(firstname,lastname,confirm_code, email, pid, rid) VALUES('$firstname','$lastname','$confirm_code', '$email', '" . $_SESSION['pid2'] . "','$ridret')";
$b = mysqli_query($mysqli,$sql);

if(!$mail->send()) {
    echo 'Message could not be sent.'; 
    echo 'Mailer Error: ' . $mail->ErrorInfo; } 
else { 
    echo "<h1>Test is sended</h1><br>";
    echo "<br><a href='dashboardcompany2.php'><button id='projectbutton'>Dashboard</button></a>
    <a href='registerrespondent2.php'><button id='projectbutton'>Add new</button></a>"; }