cache buster for AR page and TC Checkout on pantheo

functions.php

<?php

add_action( 'init', 'rt_et_bust_cache_varnish_pantheon' );

function rt_et_bust_cache_varnish_pantheon() {
	/*
	 * Set or replace $regex_path_patterns accordingly.
	 *
	 * We don't set this variable for you, so you must define it
	 * yourself per your specific use case before the following conditional.
	 *
	 * Example: anything in the /news/ directory
	 */
	$regex_path_patterns = array(
		'/attendee-registration/',
		'/tickets-checkout/',
	);

	// Loop through the patterns.
	foreach ( $regex_path_patterns as $regex_path_pattern ) {
		if ( preg_match( '#^'. $regex_path_pattern . '?#', $_SERVER['REQUEST_URI'] ) ) {
			setcookie( 'NO_CACHE', '1', time() + 0, $regex_path_pattern, $_SERVER['HTTP_HOST'] );
			// No need to continue the loop once there's a match.
			break;
		}
	}
}