demo.php

<?php

/*
Plugin Name: NinjaDemo AJAX Callbacks
Plugin URI: https://sproutapps.co/
Description: Allow for the demo form to be remotely retreived.
Author: Sprout Apps
Version: 0.8
Author URI: https://sproutapps.co
*/

function sa_try_demo_form() {
	$allowed_domains = array(
			home_url(),
			'http://sprout.dev',
			'https://sproutapps.co'
		);

	// Check to make sure that the requested origin is an allowed domain.
	// This will prevent direct access too.
	if ( in_array( $_SERVER['HTTP_ORIGIN'], $allowed_domains ) ) {
		header('Access-Control-Allow-Origin: *');
		// Form
		print do_shortcode( '[try_demo]' );
	}
	exit();
}
add_action( 'wp_ajax_nopriv_try_demo_form', 'sa_try_demo_form', 10, 0 );
add_action( 'wp_ajax_try_demo_form', 'sa_try_demo_form', 10, 0 );