标头重定向未初始化PHP

我在登录表单上遇到了一个头部重定向的小问题；虽然语句和它们都很好用，但肯定只能作为标题。我试过重定向太多的网站和页面，但仍然一无所获。非常感谢您的帮助。谢谢

  <center>
  <?php
  include './index.php';// This is a login form
  include './connection.php';// SQl connection page
  include './session.php'; // Sessions page
  error_reporting(E_ALL);
  $mysqli = new mysqli ("c3433870.co.uk.mysql", "c3433870_co_uk", "BFUWGpn3",        "c3433870_co_uk");
 if($mysqli->connect_errno > 0) {
  die('Unable to connect to database [' . $mysqli->connect_error . ']');
 }
 session_start();
 if(isset($_POST['submit'])){
    $stmt = $mysqli->prepare("SELECT username, password FROM users WHERE    username=? AND  password=? LIMIT 1");
    $username = $_POST['username'];
    $password = $_POST['password'];
    $stmt->bind_param('ss', $username, $password);
    $stmt->execute();
    $stmt->bind_result($username, $password);
    $stmt->store_result();
    if($stmt->num_rows == 1)  //To check if the row exists
        {
            while($stmt->fetch()) //fetching the contents of the row
              {
               $_SESSION['Login_sessions'] = true;
               $_SESSION['login_user'] = $username;
               header('Location: ./profile.php');

               }
        }
        else {
            echo "Wrong Username or Password!";
        }
        $stmt->close();
        $stmt->free_result();
    }
    else 
    {   
     echo "Not Found";
    }
 $mysqli->close();
 ?>
 </center>