PHP重定向仅适用于每隔一个页面

I'm trying to make two pages, where you have to go to the first page to have access to the second page. I'm doing this in WordPress and trying to add PHP code snippets to make this work. I have it working but only every other time.

I set the variable :

<?php

session_start();
$_SESSION[ 'display_page2' ] = TRUE;
?>

Page2:

<?php

session_start();

if ((isset($_SESSION['display_page2']) && $_SESSION['display_page2'] === true) || isset($_POST['nf-field-184'])) {
    //run page two
} else {
    header('Location:http://www.lytrod.com/intellicutinstallation-2/');
}
// clears the variable
unset($_SESSION['display_page2']);

else {
    header('Location:http://www.lytrod.com/intellicutinstallation-2/');
    exit();
}