Simple HTTP authentication example

// Status flag:
$LoginSuccessful = false;
 
// Check username and password:
if (isset($_SERVER['PHP_AUTH_USER']) && isset($_SERVER['PHP_AUTH_PW'])){
 
    $Username = $_SERVER['PHP_AUTH_USER'];
    $Password = $_SERVER['PHP_AUTH_PW'];
 
    if ($Username == 'jonas' && $Password == 'foobar'){
        $LoginSuccessful = true;
    }
}
 
// Login passed successful?
if (!$LoginSuccessful){
 
    /* 
    ** The user gets here if:
    ** 
    ** 1. The user entered incorrect login data (three times)
    **     --> User will see the error message from below
    **
    ** 2. Or the user requested the page for the first time
    **     --> Then the 401 headers apply and the "login box" will
    **         be shown
    */
 
    // The text inside the realm section will be visible for the 
    // user in the login box
    header('WWW-Authenticate: Basic realm="Secret page"');
    header('HTTP/1.0 401 Unauthorized');
 
    print "Login failed!\n";
 
}
else {
 
    // The user entered the correct login data, put
    // your confidential data in here: 
 
    print 'you reached the secret page!';
}