问提交表单后数据库为空

EN

<?php require('includes/config.php'); 

//if not logged in redirect to login page
if(!$user->is_logged_in()){ header('Location: login.php'); exit(); }
$uname= htmlspecialchars($_SESSION['username'], ENT_QUOTES);
if(isset($_POST['submit'])){
if (!isset($_POST['title'])) $error[] = 'Please fill out title field';
if (!isset($_POST['content'])) $error[] = 'Please fill out content field';
if (!isset($_POST['date'])) $error[] = 'Please fill out date and time field';
$title=filter_var($_POST['title'], FILTER_SANITIZE_STRING);
$content=filter_var($_POST['content'], FILTER_SANITIZE_STRING);
$postdate=$_POST['date'];

$divid = md5(uniqid(rand(),true));
$htmlcode="<style>
.demo-card-wide.mdl-card {
  width: 512px;
}
.demo-card-wide > .mdl-card__title {
  color: #fff;
  height: 176px;
  background: url('https://www.getmdl.io/assets/demos/welcome_card.jpg') center / cover;
}
.demo-card-wide > .mdl-card__menu {
  color: #fff;
}
</style>
<div class=\"demo-card-wide mdl-card mdl-shadow--2dp\" id=\"$divid\">
  <div class=\"mdl-card__title\">
    <h2 class=\"mdl-card__title-text\">$title</h2>
  </div>
  <div class=\"mdl-card__supporting-text\">
    \"$content\"<br><i class =\"material-icons\">calender_today</i>$postdate
  </div>
  <div class=\"mdl-card__actions mdl-card--border\">
    <a class=\"mdl-button mdl-button--colored mdl-js-button mdl-js-ripple-effect\">
       Done <i class=\"material-icons\">done</i>
    </a>
  </div>
  <div class=\"mdl-card__menu\">
    <button class=\"mdl-button mdl-button--icon mdl-js-button mdl-js-ripple-effect\">
      <i class=\"material-icons\">delete</i>
    </button>
  </div>
</div>";
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "events";

// Create connection
$conn = mysqli_connect($servername, $username, $password, $dbname);
// Check connection
if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}

$sql = "INSERT INTO events (user, html, divid)
VALUES ('$uname', '$htmlcode', '$divid')";

if (mysqli_query($conn, $sql)) {
    echo "New record created successfully";
} else {
    echo "Error: " . $sql . "<br>" . mysqli_error($conn);
}

mysqli_close($conn);
header("Location:events.php?action=success"); exit();}
?>

<?php
ob_start();
session_start();

//database credentials
define('DBHOST','localhost');
define('DBUSER','root');
define('DBPASS','');
define('DBNAME','registration');

//application address
define('DIR','localhost/');
define('SITEEMAIL','noreply@domain.com');

try {

    //create PDO connection
    $db = new PDO("mysql:host=".DBHOST.";charset=utf8mb4;dbname=".DBNAME, DBUSER, DBPASS);
    $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_SILENT);//Suggested to uncomment on production websites
    //$db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);//Suggested to comment on production websites
    $db->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);

} catch(PDOException $e) {
    //show error
    echo '<p class="bg-danger">'.$e->getMessage().'</p>';
    exit;
}

//include the user class, pass in the database connection
include('classes/user.php');
include('classes/phpmailer/mail.php');
$user = new User($db);
?>