gistfile1.php

<?php

/**
 * Load landing page template & register shortcodes from URL query
 *
 * @return void
 */
add_action('template_redirect', 'landing_template');
function landing_template() {
	if (get_post_type() == 'landing') {
		$template = get_field('template');
		if (isset($template)) {
			$parts = wp_parse_args($_SERVER['QUERY_STRING']);
			foreach ($parts as $key => $value) {
				add_shortcode($key, 'return_shortcode');
			}
			load_template(TEMPLATEPATH . "/single-landing-$template.php");
			exit;
		}
	}
}

/**
 * Return the value from the URL in place of a shortcode
 *
 * @return string  Querystring
 */
function return_shortcode($atts, $content, $name) {
	if (isset($name)) {
		return $_GET[$name];
	}
}