AMP: Building Accelerated Mobile Pages

Creating the server in PHP

We won't dwell on the PHP server code as it's not strictly AMP. The code we use here is the following (/ch6/signup-xhr.php):

header('Content-Type: application/json');header('Access-Control-Allow-Credentials: true');header('Access-Control-Allow-Origin: https://theampbook-com.cdn.ampproject.org');header('Access-Control-Expose-Headers: AMP-Access-Control-Allow-Source-Origin');header('AMP-Access-Control-Allow-Source-Origin: https://theampbook.com');$email = isset($_REQUEST["email"])?$_REQUEST["email"]:"";// Handle malformed email addressif(!filter_var($email, FILTER_VALIDATE_EMAIL)) {  header("HTTP/1.0 400 Error");  $content = '{"email":"'.$email .'", "message":"The email address is not valid"}';}// Pretend it's already ...