wehatepasswords.php

<?php
header("Content-Type: application/json; charset=utf-8");

$username = $_POST["username"];
$wehatepasswordsJson = $_POST["wehatepasswordsJson"];

if (empty($username)) {
    $error = "Please enter your username.";
} else if ($username !== "test") {
    $error = "This is a demo. Please enter test for the username.";
} else if (empty($wehatepasswordsJson)) {
    $error = "Please enter your password.";
} 
// At this point in script you'd compare with the pixel art JSON you saved on your server, this is just test data (it's a hollow red square)
else if ($wehatepasswordsJson !== '[{"number":1,"color":"red"},{"number":2,"color":"red"},{"number":3,"color":"red"},{"number":4,"color":"red"},{"number":5,"color":"red"},{"number":6,"color":"red"},{"number":10,"color":"red"},{"number":11,"color":"red"},{"number":15,"color":"red"},{"number":16,"color":"red"},{"number":20,"color":"red"},{"number":21,"color":"red"},{"number":22,"color":"red"},{"number":23,"color":"red"},{"number":24,"color":"red"},{"number":25,"color":"red"}]') {
    $error = "The password you entered was incorrect. Please draw a red square around the edge, but don't fill it in.";
} else {
    $error = false;
}
echo json_encode([
    "error" => $error
]);
?>