Add object caching to ACF

acf-object-caching.php

<?php
/**
 * ACF object caching
 *
 * Adds Object caching support to ACF so taht it doesn't have to recalculate all of
 * its data on each page load. It can substantially improve performance on sites that
 * heavily use ACF.
 *
 * This is NOT multisite compatible. ACF uses an alternative data structure for multisites.
 * Its internal APIs don't support an external tool to cache all of the multisite data.
 *
 * @package     Pantheon\ACF_Object_Caching
 * @author      Pantheon Professional Servies Application Performance Team
 * @license     GPL-2
 *
 * @wordpress-plugin
 * Plugin Name: ACF object caching
 * Plugin URI:  https://pantheon.io
 * Description: Adds object caching to ACF for performance gains. NOT multisite compatible.
 * Version:     1.0.0
 * Author:      Pantheon - Professional Services Application Performance Team
 * Author URI:  https://pantheon.io
 * Text Domain: TextDomain
 * License:     GPL-2
 */

namespace Pantheon\ACF_Object_Caching;

/**
 * Flush all values from the ACF cache group.
 */
function purge_acf_cache_group() {
	if ( function_exists( 'wp_cache_flush_group' ) ) {
		\wp_cache_flush_group( 'acf' );
	}
}

register_activation_hook( __FILE__, __NAMESPACE__ . '\purge_acf_cache_group' );
register_deactivation_hook( __FILE__, __NAMESPACE__ . '\purge_acf_cache_group' );

/**
 * ACF saves all of its data in runtime-only "stores" to improve performance.
 * This restores those "stores" of data that were saved in object cache.
 */
function restore_stores() {
	global $acf_stores;

	// `store_hashes` is a master list of all the stores we're, well, storing
	$store_hashes = \wp_cache_get( 'archived-store-hashes', 'acf' );

	if ( ! is_array( $store_hashes ) ) {
		return;
	}

	// Get each store's data and restore it.
	foreach ( $store_hashes as $name => $old_hash ) {
		$data = \wp_cache_get( 'archived-store:' . $name, 'acf' );

		// The crc32 algorithm is used because of speed and reliabilty for data integrity checks.
		$new_hash = hash( 'crc32c', json_encode( $data ) );

		if ( $old_hash !== $new_hash ) {
			error_log( 'ACF Object Caching: Hash mismatch for store ' . $name . ' before store generation. This store will not be restored.');
			continue;
		}

		if ( $data !== false ) {
			$store = \acf_register_store( $name, $data );

			$new_hash = hash( 'crc32c', json_encode( $store->get_data() ) );

			if ( $old_hash !== $new_hash ) {
				error_log( 'ACF Object Caching: Hash mismatch for store ' . $name . ' after store generation. This store will be deleted.');
				unset( $acf_stores[ $name ] );
			}
		}
	}
}

/**
 * At the end of the process, take all the stores that have been created and save them.
 */
function save_stores() {
	if ( ! apply_filters( 'acf-object-caching-save-stores', true ) ) {
		return;
	}

	global $acf_stores;

	$new_stores = array_keys( $acf_stores );

	// List of stores that shouldn't be cached.
	$uncacheable_stores = apply_filters( 'acf-object-caching-uncacheable-stores', [ 'notices' ] );

	// Combine our previous list of stores with the stores from this request.
	$store_hashes = \wp_cache_get( 'archived-store-hashes', 'acf' );
	$store_hashes = is_array( $store_hashes ) ? $store_hashes : [];

	// Remove uncacheable stores from the list.
	foreach ( $new_stores as $key => $store ) {
		if ( in_array( $store, $uncacheable_stores, true ) ) {
			unset( $new_stores[ $key ] );
		}
	}

	// Save each store to the object cache.
	foreach ( $acf_stores as $name => $store ) {
		\wp_cache_set( 'archived-store:' . $name, $store->get_data(), 'acf' );
		$store_hashes[ $name ] = hash( 'crc32c', json_encode( $store->get_data() ) );
	}

	// Save our master list of stores to object cache.
	\wp_cache_set( 'archived-store-hashes', $store_hashes, 'acf' );

}

/**
 * Purge the ACF values cache for a specific post.
 */
function purge_post_cache( $post_id ) {
	$values = \wp_cache_get( 'archived-store-values', 'acf', false, $found );

	// If we don't have a cached value, abort.
	if ( ! $found ) {
		return;
	}

	$values = is_array( $values ) ? $values : [];

	// Loop through the values. If the key matches our pattern, remove it.
	// For example, the pattern for field "date" on post number "123" is 123:date
	foreach ( $values as $key => $value ) {
		if ( strpos( $key, $post_id . ':' ) === 0 ) {
			unset( $values[ $key ] );
		}
	}

	// Set the stripped down values.
	\wp_cache_set( 'archived-store-values', $values, 'acf' );

	$stores = \wp_cache_get( 'archived-store-hashes', 'acf' );

	if ( is_array( $stores ) ) {
		$stores['values'] = hash( 'crc32c', json_encode( $values ) );

		\wp_cache_set( 'archived-store-hashes', $stores, 'acf' );
	}
}

// On init, restore the stores. Priority 6 to be compatible with ACF.
add_action( 'init', __NAMESPACE__ . '\restore_stores', 6 );
// On shutdown, save the stores. Priority 99 to make sure it fires late in the process.
add_action( 'shutdown', __NAMESPACE__ . '\save_stores', 99 );
// On save, delete the cached values for a post.
add_action( 'acf/save_post', __NAMESPACE__ . '\purge_post_cache' );
// On delete, delete the cached values for a post.
add_action( 'delete_post', __NAMESPACE__ . '\purge_post_cache' );