WP: MU Plugin for Optimizing AJAX calls.

wps-mu-ajax,php

<?php
/**
 * Plugin Name:     WPS AJAX MU Plugin
 * Plugin URI:      https://wpsmith.net
 * Description:     Improves the performance of AJAX requests.
 * Author:          Travis Smith <t@wpsmith.net>
 * Author URI:      https://wpsmith.net
 * Version:         0.0.1
 *
 * The main mu plugin file.
 *
 * This file is read by WordPress to generate the plugin information in the plugin
 * admin area. This file also includes all of the dependencies used by the plugin,
 * registers the activation and deactivation functions, and defines a function
 * that starts the plugin.
 *
 * You may copy, distribute and modify the software as long as you track
 * changes/dates in source files. Any modifications to or software including
 * (via compiler) GPL-licensed code must also be made available under the GPL
 * along with build & install instructions.
 *
 * PHP Version 7.2
 *
 * @category   WPS\WP\Plugins\Mu\AJAX
 * @package    WPS\WP\Plugins\Mu\AJAX
 * @author     Travis Smith <t@wpsmith.net>
 * @copyright  2020 Travis Smith
 * @license    http://opensource.org/licenses/gpl-2.0.php GNU Public License v2
 * @link       https://wpsmith.net/
 * @since      0.0.1
 */

namespace WPS\WP\Plugins\Mu\AJAX;

add_filter( 'option_active_plugins', __NAMESPACE__ . '\ajax_disable_plugins', PHP_INT_MAX );
/**
 * Intercept `get_option( 'active_plugins' )` to only load certain plugins.
 *
 * @param array $plugins Array of active plugins.
 *
 * @return array Array of a plugins that should be activated.
 */
function ajax_disable_plugins( $plugins ) {

	// Do nothing if it's not AJAX or abiding by `fast_ajax` element.
	// Load all plugins if (1) not in ajax mode, (2) fast_ajax is not set, & (3) fast_ajax is set to false.
	// phpcs:ignore WordPress.Security.NonceVerification.Recommended
	if ( ! defined( 'DOING_AJAX' ) || ! isset( $_REQUEST['fast_ajax'] ) || ( isset( $_REQUEST['fast_ajax'] ) && ! (bool) $_REQUEST['fast_ajax'] )
	) {
		return $plugins;
	}

	// Disable all plugins if none are told to load by the load_plugins array.
	// phpcs:ignore WordPress.Security.NonceVerification.Recommended
	if ( ! isset( $_REQUEST['load_plugins'] ) || ( ! isset( $_REQUEST['load_plugins'] ) && ! (bool) $_REQUEST['load_plugins'] ) ) {
		return array();
	}

	// Unset plugins not included in the load_plugins array.
	// phpcs:ignore WordPress.Security.NonceVerification.Recommended
	return array_intersect( $plugins, array_map( 'sanitize_text_field', wp_unslash( $_REQUEST['load_plugins'] ) ) );
}