create.php

<?php

$timestamp = date('Y-m-d H:i:s', time());

if (isset($_POST['name']) && isset($_POST['description']) && isset($_POST['created_at'])) {

    $pdo = new PDO("mysql:host=127.0.0.1;dbname=article", 'dbuser', '123');
    $stmt = $pdo->prepare('INSERT INTO article (name, description, created_at) VALUES (:name,:description,:created_at)');
    $stmt->bindValue(':name', $_POST['name']);
    $stmt->bindValue(':description', $_POST['description']);
    $stmt->bindValue(':created_at', $_POST['created_at']);

    $stmt->execute();

    header('Location: index.php');
}

?>

<form method="post">
    <input type="text" required name="name" placeholder="name">
    <br>
    <input type="text" required name="description" placeholder="description">
    <br>
    <input type="text" required name="created_at" placeholder="created_at" value="<?php echo $timestamp ?>">
    <br>
    <input type="submit">
</form>