Mysql database doesn't receive form content

Hi! I just started working with PHP and I followed a simple tutorial online to create a form but it isn't working.I have an account on 1&1, i created the database there and the table.When I submit the form it works with no errors but when i check the table online nothing is there.

I double checked my table and my row has the same name so it is ok.

Any help would be greatly appreciated!

My form:

<form action="demo.php" method="post"/>

<p>Input 1: <input type="text" name="input1"/></p>

<input type="submit" value="Submit"/>

</form>

demo.php:

<?php

    $host_name  = "blablabla";

    $database   = "blablabla";

    $user_name  = "blablabla";

    $password   = "blablabla";

    $connect = mysqli_connect($host_name, $user_name, $password, $database);

    if(mysqli_connect_errno())

    {

    echo '<p>Verbindung zum MySQL Server fehlgeschlagen: '.mysqli_connect_error().'</p>';

    }

    else

    {

    echo '<p>Verbindung zum MySQL Server erfolgreich aufgebaut.</p>';

    }

    $value=$_POST['input1'];

    $sql = "INSERT INTO demo (input1) VALUES ('$value')";

    mysqli_close();

?>