verstuurInschrijving.php
<?php
session_start();
$toMail = $_POST['email'];
$to      = $toMail;
$subject = 'Inschrijving item';
$message = $_POST['bericht'];
$headers = 'From: saxiontopicusservice@saxion.nl' . "\r\n" .
    'Reply-To: saxiontopicusservice@saxion.nl' . "\r\n" .
    'X-Mailer: PHP/' . phpversion();

mail($to, $subject, $message, $headers);
?>

###################

<?php
require 'header.php';
$itemId = $_GET['id']
?>

    <!-- Updates Section -->
    <section class="updates section-padding">
        <div class="container-fluid">
            <div class="row">
                <div class="col-lg-12 col-md-12">
                    <!-- Recent Updates            -->
                    <div class="wrapper recent-uodated">
                        <?php
                        $servername = "localhost";
                        $username = "root";
                        $password = "root";
                        $dbname = "project";
                        $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
                        $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

                        $stmt = $conn->prepare("SELECT * FROM item WHERE itemId='$itemId'");
                        $stmt->execute();
                        $obj = $stmt->fetch();
                        ?>

                        <div id="new-updates" class="card-header d-flex justify-content-between align-items-center">
                            <h2 class="h5 display"><?php echo $obj['titel'] ?></h2>
                        </div>

                                <!-- Item-->
                                <li class="d-flex justify-content-between">
                                    <?php

                                        echo '<div>
                                                   <p>'.$obj['beschrijving'].'</p>
                                                   <p><strong>Aantal uur:</strong> '.$obj['aantalUur'].'</p>
                                                   <p><strong>Datum:</strong> '.$obj['gevraagdeDatum'].'</p>
                                                   <p><strong>Contactpersoon:</strong> '.getUserAttribute($obj['userId'], 'voornaam'). ' ' . getUserAttribute($obj['userId'],'achternaam') . '</p>
                                                </div>'
                                    ?>
                                </li>
                                <div class="card">
                                    <div id="new-updates" class="card-header d-flex justify-content-between align-items-center">
                                        <h2 class="h5 display"><a data-toggle="collapse" data-parent="#accordion" href="#contact" aria-expanded="true" aria-controls="contact">Neem contact op</a></h2>
                                    </div>
                                    <div id="contact" role="tabpanel" class="collapse">
                                    <div class="card-block">
                                        <p>Contact mail:</p><?php $obj['contactMail'] ?>
                                        <p>Contact Telefoon:</p><?php $obj['contactTelefoon'] ?>
                                        <br>
                                        <form action="verstuurInschrijving.php">
                                            <div class="form-group">
                                                <label for="email">Versturen vanaf:</label>
                                                <input disabled type="email" name="email" class="form-control" id="email" value="<?php echo $_SESSION['email']?>" style="width: 200px">
                                            </div>
                                            <div class="form-group">
                                                <label for="pwd">Bericht:</label>
                                                <textarea rows="8" id="pwd" cols="70" name="bericht" class="col-md-11 form-control form-control"></textarea>

                                            </div>
                                            <div class="checkbox">
                                                <label><input type="checkbox" name="kopie" checked="checked"> Stuur kopie naar eigen mail</label>
                                            </div>
                                            <button type="submit" class="btn btn-outline-success">Inschrijven</button>
                                        </form>
                                    </div>
                                </div>
                            </ul>
                        </div>
                    </div>
                </div>
            </div>
        </div>
    </section>
    <footer class="main-footer">
        <div class="container-fluid">
            <div class="row">

            </div>
        </div>
    </footer>
</div>
<!-- Javascript files-->
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js"></script>
<script src="js/tether.min.js"></script>
<script src="js/bootstrap.min.js"></script>
<script src="js/jquery.cookie.js"> </script>
<script src="js/grasp_mobile_progress_circle-1.0.0.min.js"></script>
<script src="js/jquery.nicescroll.min.js"></script>
<script src="js/jquery.validate.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.5.0/Chart.min.js"></script>
<script src="js/charts-home.js"></script>
<script src="js/front.js"></script>

</body>
</html>