使用PHP Mailer发送firstname lastname

I made a form that request your name, last name, email and motivation for applying for a internship. I made a PHP file for sending all the information with PHPmailer.

The funny things that's happening is, that lastname isn't sent with name, email and motivation($comments).

Sample code from the form.

<div id="contactform">
<form method="post" action="sendmail.php">

        <p><label for="name">Naam:*</label> <input type="text" name="name"  id="name" tabindex="1" /></p>
        <p><label for="lastname">Achternaam:*</label> <input type="text" name="lastname" id="lastname" tabindex="2" /></p>



        <p><label for="email">Email:*</label> <input type="text" name="email" id="email" tabindex="3" /></p>
        <p><label for="comments">Motivatie:*</label> <textarea name="comments" id="comments" cols="12" rows="6" tabindex="4"></textarea></p> 


</br><br>

        <p><input type="submit" class="button radius medium" name="submit" id="submit" value="submit" tabindex="5" /></p>

And this is the sample code from the sendmail.php

<?php

$name = trim($_POST['name']);
$lastname = trim($_POST['lastname']);
$email = $_POST['email'];
$comments = $_POST['comments'];
$site_owners_email = 'info@inperfection.nl'; // Replace this with your own email address
$site_owners_name = 'CloudMe'; // replace with your name

if (strlen($name) < 2) {
    $error['name'] = "Please enter your name";  
}

if (strlen($lastname) < 2) {
$error['lastname'] = "Trolololololololo.";
}



if (!preg_match('/^[a-z0-9&\'\.\-_\+]+@[a-z0-9\-]+\.([a-z0-9\-]+\.)*+[a-z]{2}/is', $email)) {
    $error['email'] = "Please enter a valid email address"; 
}

if (strlen($comments) < 4) {
    $error['comments'] = "Please leave a comment.";
}

if (!$error) {

    require_once('phpMailer/class.phpmailer.php');
    $mail = new PHPMailer();

    $mail->From = $email;
    $mail->Subject = "Contact Form";
    $mail->AddAddress($site_owners_email, $site_owners_name);
    $mail->Body = "Naam :$name Achternaam:$lastname Email:$email Motivatie:$comments";

    $mail->Send();

    echo "<div data-alert class='alert-box success'>Thanks " . $lastname . ". Your message has been sent.<a href='#' class='close' onclick='clearForms()'>&times;</a></div>";

} # end if no error
else {

    $response = (isset($error['name'])) ? "<div class='alert-box alert'>" . $error['name'] . "</div> 
" : null;
    $response = (isset($error['lastname'])) ? "<div class='alert-box alert'>" . $error['lastname'] . "</div> 
" : null;
    $response .= (isset($error['email'])) ? "<div class='alert-box alert'>" . $error['email'] . "</div> 
" : null;
    $response .= (isset($error['comments'])) ? "<div class='alert-box alert'>" . $error['comments'] . "</div>" : null;

    echo $response;
} # end if there was an error sending
?>

So, the variable is set for $lastname. But am I overlooking something?

Help would be great.