navigatie

<?php 
  $page = $_GET['page']; 
  if($page){  
  $site = file_exists($page.'.php') ? $page.'.php' : 'error.php';}
  else{
  $site = 'home.php';        
  }
  include($site);
  ?> 

<?php 
  $page = $_GET['page']; 
  if($page){  
  $site = file_exists($page.'.php') ? $page.'.php' : 'error.php';}
  else{
  $site = 'home.php';        
  }
  include($site);
  ?>

<?php
$a = 1;
require 'pagina.php';

<?php
$a = 1;
require 'pagina.php';

<?php
if(!isset($a)) die("...");

<?php
if(!isset($a)) die("...");