Simple Endpoint Plugin

icreate-simple-endpoint.php

<?php
/*
Plugin Name: iCreate Simple Endpoint
Description: Simple way to add a landing page endpoint
Author: iCreate Advertising
Version: 1.0.0
Author URI: https://icreateadvertising.com.au
*/

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}


// CONFIG LANDING PAGE ENDPOINT

//remember to flush rewrite rules if you change the endpoint
define( 'IC_LANDING_ENDPOINT', 'lp' );

// END CONFIG


add_action( 'init', 'ic_ep_endpoint' );
add_filter( 'body_class', 'ic_ep_body_class' );

register_deactivation_hook( __FILE__, 'flush_rewrite_rules' );
register_activation_hook( __FILE__, 'ic_ep_flush_rewrites' );
function ic_ep_flush_rewrites() {
	ic_ep_endpoint();
	flush_rewrite_rules();
}


function ic_ep_endpoint() {
	add_rewrite_endpoint( IC_LANDING_ENDPOINT, EP_ALL );
}

function ic_ep_body_class( $classes ) {
	if ( ic_is_landing() ) {
		$classes[] = 'landing-page';
	}

	return $classes;
}

function ic_is_landing() {
	global $wp_query;

	return isset( $wp_query->query_vars[ IC_LANDING_ENDPOINT ] );
}