Argthtjtr

I have a page titled login.php, if a user successfully logs in, then he is redirected to map.php. There is also a hyperlink on login.php to map.php

map.php starts as follows:

 <?php 

 session_start();

 if ($_SESSION){

 ?>

then output a bunch of HTML and JAVASCRIPT then...

 <?php } else {

 header ('Location: ../login.php');

 exit();

 $message = "wrong answer";

 echo "<script type='text/javascript'>alert('$message'); 

 </script>";

 }

 ?>

If I start on login.php, and then click on the hyperlink to jump to the map without entering a username and password I see that the browser is refreshed and I have redirected myself back to the same page as desired, however how do I get the alert to work? I wish to let the user know that he must be logged in in order to view map.php

i wish to let the user know that he must be logged in in order to see the map.

You have mainly two different solutions to be able to handle the redirect.

Handle the redirect with PHP

Instead of showing an alert, you can output a normal text and use the refresh header call in combination with the url header call in order to send a header to the client browser that refresh the page after a certain number of seconds.

<?php

}

else

{

    $message = "wrong answer";

    header('Refresh: 5; url=login.php'); 

    exit($message);

}

Handle the redirect with Javascript

Just output the alert script that you have already written and then handle the redirect through javascript instead of using header() PHP function.

<?php

}

else

{

    $message = "wrong answer";

    echo "<script>

    alert('$message');

    window.location.href='login.php';

    </script>";

    exit;

}

I personally recommend to handle the redirect through PHP, since it is more elegant as solution and because you will not have to worry about users that have JavaScript disabled in their browser.