if ($stmt->execute()):
    echo 'Well done! You have successfully registered with us!';
  else:
    echo 'There seems to be an issue getting you registered.';

<?php

ini_set('display_errors', 'On');
ini_set('html_errors', 0);
error_reporting(-1);

require 'connection.php';

$message = '';

if (!empty($_POST['username']) && !empty($_POST['password'])):

  // $username = $_POST['username'];
  $password = $_POST['password'];
  $confirmpassword = $_POST['confirmpassword'];

//var_dump($password, $confirmpassword);

  if($password == $confirmpassword):

  $sql = "INSERT INTO users (FirstName, LastName, Role, Email, Username, Password) VALUES (:firstname, :lastname, :role, :email, :username, :password)";
  $stmt = $conn->prepare($sql);
  $hashPassword = password_hash($password, PASSWORD_DEFAULT);

  $stmt->bindParam(':firstname', $_POST['firstname']);
  $stmt->bindParam(':lastname', $_POST['lastname']);
  $stmt->bindParam(':role', $_POST['role']);
  $stmt->bindParam(':email', $_POST['email']);
  $stmt->bindParam(':username', $_POST['username']);
  $stmt->bindParam(':password', $hashPassword);

  if ($stmt->execute()):
    echo 'Well done! You have successfully registered with us!';
    //$message = 'Well done! You have successfully registered with us!';
    //header('Location:loginPage.php');
  else:
    echo 'There seems to be an issue getting you registered.';
    //$message = 'There seems to be an issue getting you registered.';
  //else:
    //echo 'Your passwords do not match!';
    //$message = 'Your passwords do not match, please enter them correctly.';

endif;

endif;

endif;

--><form class="col-1-3" action="register.php" method="post">

<fieldset class="register-group">

  <label>
    <br>First Name*
    <input type="text" name="firstname" placeholder="FirstName" value="<?php echo $firstname; ?>">
  </label>

  <label>
    Last Name*
    <input type="text" name="lastname" placeholder="LastName" value="<?php echo $lastname; ?>">
  </label>

  <label>
    Role*
    <select name="role">
      <option value="Student" selected>Student</option>
      <option value="Tutor" selected>Tutor</option>
      <option value="Admin" selected>Admin</option>
    </select>
  </label>

<label>
  Email Address*
  <input type="email" name="email" placeholder="Email"  value="<?php echo $email; ?>">
</label>

<label>
  Choose a Username*
  <input type="text" name="username" placeholder="Username" value="<?php echo $username; ?>">
</label>

<label>
  Choose a Password*
  <input type="password" name="password" placeholder="Password">
</label>

<label>
  Repeat Password*
  <input type="password" name="confirmpassword" placeholder="Confirm Password">
</label>

  <input class="btn btn-default" type="submit" name="register" value="Register">

</form>

if (!empty($_POST['username']) && !empty($_POST['password'])):
    //...
    if($password == $confirmpassword):
        //...
        if ($stmt->execute()):
            echo 'Well done! You have successfully registered with us!';
            //...
        else:
            echo 'There seems to be an issue getting you registered.';
            //...
        endif;
    else:
        echo 'Your passwords do not match!';
        //...
    endif;
endif;