HTML Code - where to put the files

I am on openhab 2.5.1.
To protect some system functions I would like to implement a password protection - created a password entry screen:

password.html:

<html>

<form name="login" action="login.php" method="post">
    Login Passwort: 
 <input type="password" name="passwort" value="" />
 <input type="submit" value="Login" name="Login" />
</form>

login.php:

<?php
// login.php
$Passwort = "123456";
$Uebernahme = $_POST['passwort']; // Die Übernahme des eingegebenen Passwortes

// Nun die Abfrage:
if($Uebernahme == $Passwort)
{
 echo'Das eingegebene Passwort ist richtig';
}
else
{
 echo'Das eingegebene Passowrt ist falsch.<br />';
 echo'Bitte gehen Sie <a href="javascriopt:history.back()">zurück</a> und versuchen Sie es erneut';
 // Hier, wenn das Passwort falsch ist, soll ein Zurücklink erscheinen
}
?>

with the login.php I would like to test if the password is correct and do further actions.
After I press Enter it receive following answer:

HTTP ERROR 404

Problem accessing /static/login.php. Reason:

    Not Found

Powered by Jetty:// 9.4.20.v20190813

The login.php is in the same folder as my password.html (openHAB-conf/html).
What is wrong - where do I have to place the login.php file.
Thanks for any hint.
Georg

I’m no Jetty expert by any measure but it looks like the OH Jetty implementation doesn’t support FastCGI to run PHP out of the box.
More knowledgeable community members can probably tell you how to enable it…

Thanks Ron!
You are right - the error message is misleading. Actually if I start a separate php-server to test it everything works fine.
Would appreciate if I could receive some hints how to configure jetty to support FastCGI.
Georg