Class 'PHPMailer' not found in /home/treehouse/workspace/suggest.php:17

<?php 


if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $name = trim(filter_input(INPUT_POST,"name",FILTER_SANITIZE_STRING));
    $email = trim(filter_input(INPUT_POST,"email",FILTER_SANITIZE_EMAIL));
    $details = trim(filter_input(INPUT_POST,"details",FILTER_SANITIZE_SPECIAL_CHARS));

    if ($name == "" || $email =="" || $details == "") {
      echo "Please fill in the required fields: Name, Email and Details";
      exit;
    }
    if ($_POST["address"] != "") {
      echo "Bad form input";
      exit;
    }
  if (!PHPMailer::validateAddress($email)){
    echo "Invalid Email Address";
    exit;
  }

    echo "<pre>";
      $email_body = "";
      $email_body .= "Name " . $name . "\n";
      $email_body .= "Email " . $email . "\n";
      $email_body .= "Details " . $details . "\n";
    echo $email_body;
    echo "</pre>";

    //To Do: Send email
    header("location:suggest.php?status=thanks");
}

$pageTitle = "Suggest a Media Item";
$section = "suggest";

include("inc/header.php"); ?>

<div class="section page">
  <div class="wrapper">
    <h1>Suggest a Media Item</h1>
    <?php if (isset($_GET["status"]) && $_GET["status"] == "thanks") {
        echo "<p>Thanks for the email! I&rsquo;ll check out your suggestion shortly!</p>";
     } else { ?>
    <p> If you thnk there is something I&rsquo;m missing, let me know! Complete the form to send me an email.</p>
    <form method="post" action="suggest.php">
      <table>
        <tr>
          <th><label for="name">Name</label></th>
          <td><input type="text" id="name" name="name" /></td>
        </tr>
        <tr>
          <th><label for="email">Email</label></th>
          <td><input type="text" id="email" name="email" /></td>
        </tr>
        <tr>
          <th><label for="details">Suggest Item Details</label></th>
          <td><textarea name="details" id="details"></textarea></td>
        </tr>
        <tr style="display:none">
          <th><label for="address">Email</label></th>
          <td><input type="text" id="address" name="address" />Please leave this field blank.</td>
        </tr>
      </table>
      <input type="submit" value="Send" />

    </form>
    <?php } ?>
  </div>
</div>

<?php include("inc/footer.php"); ?>