acf-hooks-basic.php

acf-hooks-basic.php

<?php

/**
 * Hook before acf_get_value() queries the DB.
 */
add_filter(
	'acf/pre_load_value',
	function( $meta, $object_id, $field ) {

		// Initiate the ACF 'values' store.
		$store = acf_get_store( 'values' );

		// "prefetched:$object_id" is just to mark that I have previously fetched it.
		if ( ! $store->has( "prefetched:$object_id" ) ) {

			// Depending on ACF usage this field could be coming from meta or categories.
			// For simplicity, lets go basic config only applied to post types.
			$meta_type = 'post';

			// Get all the object's meta. Could cache this,
			// but it will be marked as prefetched, so won't run this
			// more than once.
			$meta_data = get_metadata( $meta_type, $object_id );

			// Time to populate the "values" ACF store.
			foreach ( $meta_data as $field_name => $value ) {

				// Force singleness of individual values.
				$real_value = is_array( $value ) && 1 === count( $value ) ? array_pop( $value ) : $value;

				// Ignore hidden keys. Its an ACF thing.
				if ( preg_match( '/^_/', $field_name ) ) {
					continue;
				}

				// Where the magic happens.
				$store->set( "$object_id:$field_name", $real_value );
			}

			// Mark it as "done"!
			$store->set( "prefetched:$object_id", true );
		}

		// If value is already fetched then return that value.
		$field_name = $field['name'];
		if ( $store->has( "$object_id:$field_name" ) ) {
			return $store->get( "$object_id:$field_name" );
		}

		// Fallback to ignore prefetching and let ACF do things the ACF way.
		return $meta;
	},
	10,
	3
);

/**
 * Other possible things:
 *
 * 1. Hook `acf/pre_update_value` action to save meta differently (or elsewhere entirely).
 * 2. Fetch meta from a different source.
 * 3. Hook `acf/load_field` to remove further calls to DB.
 */