尝试将数据从表单插入数据库时​​出错[重复]

我对php和数据库很陌生。我正在尝试创建一个表单，并从表单中获取数据并将其插入数据库中。我认为它可以成功地与数据库建立连接，但是当它应该从表格中获取数据并插入数据库中时什么也没发生。只需打开一个新页面，在其中写“成功连接”即可。

<div class="login">
    <div class="box">
        <form action="post" class="form-box">
            <h3>Login</h3>
            <input type="email" placeholder="E-mail">
            <input type="password" placeholder="Password">
            <input type="submit" value="Sign in" class="form-button">
            <a href="#">Forgot yor password?</a>
        </form>
    </div>
</div>

<div class="register">
    <div class="box">
        <!-- <form action="core/init.php" method="post" class="form-box"> -->
        <form  method="post" class="form-box">
            <h3>Create Account</h3>
            <!-- <input type="text" placeholder="First Name*">
            <input type="text" placeholder="Last Name*"> -->
            <input type="email" placeholder="Email*"  name="email">
            <input type="password" placeholder="Password*" name="pass">
            <input type="password" placeholder="Retype Password*" name="re_password">
            <!-- <input type="checkbox" name="subscribe" class="input-inline"><label for="subscribe" >Subscribe here</label> -->
            <input type="submit" value="Submit" class="form-button" name="registerUser">
        </form>
    </div>
</div>

    <?php
$servername = "localhost";
$username = "xxxxx";
$password = "xxxxx";

try {
  $conn = new PDO("mysql:host=$servername;dbname=xxxxxx", $username, $password);
  // set the PDO error mode to exception
  $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
  echo "Connected successfully";
} catch(PDOException $e) {
  echo "Connection failed: " . $e->getMessage();
}

if(isset($_POST['registerUser'])){
    $email      = $_POST['email'];
    $password   = $_POST['pass'];
    $re_password= $_POST['re_password'];

    if($password === $re_password){
        $sql = "INSERT INTO users (email, pass) VALUES (?,?)";
        $stmtinsert = $db->prepare($sql);
        $result = $stmtinsert->execute([$email,$password]);
        if($result){
            echo 'Succes';
        }else{
            echo 'data error';
        }
    }else{
        echo "Password doen't match";
    }

}

?>

我发布了我的html和php代码。有谁能够帮助我？

谢谢