Im getting this notice on my executing website:

`Notice: Undefined variable: _SESSION in *PATH* on line 25` which is this line of code `$_SESSION["Registration_Error"] = TRUE;` why is the $\_SESSION-Variable unkown?

Do they changed the way one can save data in the Session-Variable/Cookie?

Haven't found something good on Google. Just this <http://php.net/manual/de/book.session.php#116217> and I dont think that this helps much.

Ideas?

EDIT:

Full Code

```
<?php

session_start();

function __autoload($class_name) {
    include "../backend/classes/$class_name.php";
}

$Connection = new DB_Connect();
$User_Functions = new User_Functions();

$UserName = filter_input(INPUT_POST, "UserName");
$Password = filter_input(INPUT_POST, "Password");
$Mail = filter_input(INPUT_POST, "Mail");
$date = new DateTime();
$Registration_Date = $date->format("Y-m-d H:i:s");

if (!empty($UserName) && !empty($Password) && !empty($Mail)) {
    if (!$User_Functions->User_Exists($UserName)) {
        $Password_hashed = password_hash($Password, PASSWORD_DEFAULT);

        $Query = "INSERT INTO wordsusers (`wordsUserName`, `wordsUserPassword`, `wordsUserMail`, `wordsUserRegDate`) VALUES (:wordsUserName, :wordsUserPassword, :wordsUserMail, :wordsUserRegDate)";
        $Parameter = array(":wordsUserName" => $UserName, ":wordsUserPassword" => $Password_hashed, ":wordsUserMail" => $Mail, ":wordsUserRegDate" => $Registration_Date);
        $Registered = $Connection->Execute_PDO_Command($Query, $Parameter);
    } else {
        $_SESSION["Registration_Error"] = TRUE;
        header("Location: ../index.php");
    }
}

```