I've made this code to login in to a site, but my code always returns `Onjuiste gegevens`*(incorrect data)*. I don't know why.

In my database I have made 1 account with username: sander and password: sander. When I enter this in the form I still get "Onjuiste gegevens". Could someone please help me to fix this?

```php
<?php
$conn = mysqli_connect("localhost", "root", "", "login");

if (isset($_POST['inloggen'])) {
    $username = $_POST['username'];
    $password = $_POST['password'];

    $query = "SELECT * FROM users WHERE username = '$username' AND '$password'";

    $result = mysqli_query($conn, $query);

    if (mysqli_num_rows($result) == 1) {
        echo "Juiste gegevens!";
    } else {
        echo "Onjuiste gegevens!";
    }

    echo "<br />";
}
?>
<form method="post" action="">
    <label>Username</label>
    <input type="text" name="username"/><br />
    <label>Password</label>
    <input type="password" name="password"/><br />

    <input type="submit" name="inloggen" value="Inloggen"/>

</form>

```