generating a random number and send to the header

In my login form, if email or password is wrong I set header ('Location: login.php?Err=284613');. Then using Javascript I capture it and give the error code to the page using if (window.location.search == "?Err=284613"){}.

The issue is that I don't want the user to type login.php?Err=284613 and trigger the error code manually.

Can I generate random numbers with PHP and show different numbers each time in login.php?Err="random numbers". Of course, then I need to capture that random number with javascript in order to show the error on the page.

<?php
if (!isset($_POST['username'], $_POST['password']))
{
    exit('Please fill both the username and password fields!');
}

if ($stmt = $con->prepare('SELECT id, Password FROM users WHERE Email = ?'))
{
    $stmt->bind_param('s', $_POST['username']);
    $stmt->execute();

    $stmt->store_result();
    if ($stmt->num_rows > 0)
    {
        $stmt->bind_result($id, $password);
        $stmt->fetch();
        if (password_verify($_POST['password'], $password))
        {

            session_regenerate_id();
            $_SESSION['loggedin'] = true;
            $_SESSION['name'] = $_POST['username'];
            $_SESSION['id'] = $id;
            header('Location: index.php');

        }
        else
        {

            header('Location: login.php?Err=284613');

        }
    }
    else
    {

        header('Location: login.php?Err=284613');

    }

    $stmt->close();
}
}

?>

    
if(window.location.search == "?Err=284613")
{
    
 setError(email, 'Wrong Password!');
    
}

source https://stackoverflow.com/questions/70550542/generating-a-random-number-and-send-to-the-header