PHP Captcha Form - php

Question

I have a Google App Engine PHP website. I have a page with the following recaptcha form:
<?php
ob_start();
if($_SERVER["REQUEST_METHOD"] === "POST")
{
//verify captcha
$recaptcha_secret = "6LfkBQMTAAAAABN5yEqoqxoLqKOBKIvoCHZ-3vP3";
$response = file_get_contents("https://www.google.com/recaptcha/api/siteverify?secret=".$recaptcha_secret."&response=".$_POST['g-recaptcha-response']);
$response = json_decode($response, true);
while (ob_get_status())
{
ob_end_clean();
}
if($response["success"] === true)
{
echo '<META HTTP-EQUIV="Refresh" Content="0; URL=register.php">';
exit;
}
else
{
echo "Please try again";
}
}
?>
Once the user types in the correct recaptcha they are sent to 'register.php'. This all works fine and the user is sent correctly. But the problem is the user can just type 'register.php' into the URL and access it. I am trying to make it that the user can only access this page if the recaptcha has been entered. (The recaptcha is on a different page to 'register.php').
I am using sessions, when the user is logged in, so have this on register.php and this needs to stay there:
<?php
session_start();
if ( !isset($_SESSION['username']) )
{
header("Location:error.php");
exit();
}
?>
Is there a way to do something like:
<?php
session_start();
if ( !isset($_SESSION['username']) )
{
header("Location:error.php");
exit();
}
and ($response["success"] === false)
header("Location:error.php");
exit();
}

Answer 1

Seems like you're looking for the Or logical operator, save the value before the redirect:
if($response["success"] === true)
{
$_SESSION['success'] = true;
echo '<META HTTP-EQUIV="Refresh" Content="0; URL=register.php">';
exit;
}
And now add a new check:
<?php
session_start();
if ( !isset($_SESSION['username']) || $_SESSION['success'] != true )
{
header("Location:error.php");
exit();
}
?>
If any of those expressions is true then the error block will be executed.