Page navigation with php

Question

I am trying to create a dynamic website, the index.php includes the following code in the content area of the website:

<?PHP

// if undefined then define
 if(!$od || $od == ""){
 $od = "news";
 }
// check if exists prep
 $link = 'incs'."/".$od.$ext;
 flush();
 $fp = fopen($link, "r");

// check if inclusion file not exists then return error
 if (!$fp) {
 echo "An error has ocurred while processing your request. The file linked as ?od=".$od." does not appear to exist.";
 }

// if exists then return parse
 else { 
 fclose($fp);
 include 'incs'."/".$od.$ext;
 }

echo '</body>'."\n";
echo '</html>'."\n";

?>

I also have various links throughout the site to pages like register, login, etc. Those links point to pages like ?od=register, ?od=login, etc.

The website will pull the default file for me, news, and display that in my content section of my website, but when I click register, the url in the address bar DOES change to /?od=register, but the default news remains in the content section, is there an error in the code above? Or am I just missing something?

P.S. $ext is defined in my config file as inc.php, which is included at the top of the index page.

Answer 1

I believe you need to define $od with a $_GET['od'] or $_REQUEST['od']

$od = $_GET['od'];
// if undefined then define
 if(!$od || $od == ""){
 $od = "news";

Answer 2

Besides the fact that this is very insecure - you are making a GET request, access the variables through the $_GET array ie $od = $_GET['od']