WP custom AJAX handler

ajax.php

<?php
// Custom AJAX Handler
// watch https://coderwall.com/p/of7y2q/faster-ajax-for-wordpress

/* Route functions place in functions.php or mu-plugin
function wp_pretty_ajax()
{
	add_rewrite_rule('ajax$', 'ajax.php', 'top');
}
*/

//mimic the actual admin-ajax
define('DOING_AJAX', true);

 
// AJAX Custom Handler
ini_set('html_errors', 0);
define('SHORTINIT', true);


require_once __DIR__ . '/wp-load.php';

/** For JSON Response
$return = array(
	'message'   => 'Saved',
	'ID'        => 1
);
// https://wp-kama.ru/function/wp_send_json
wp_send_json($return, null, JSON_UNESCAPED_UNICODE | JSON_PRETTY_PRINT);
*/
 
/* For HTML Response */
//Typical headers
header('Content-Type: text/html');
send_nosniff_header();

//Disable caching
header('Cache-Control: no-cache');
header('Pragma: no-cache');

//Include only the files and function we need
require_once  ABSPATH . WPINC . '/formatting.php';
require_once  ABSPATH . WPINC . '/meta.php';
require_once  ABSPATH . WPINC . '/post.php';
wp_plugin_directory_constants();

//and do your stuff
// Return HTML for example for HTMX!
echo '<h2>Hello</h2>';