Cache sucess API responses in WordPress.

cache-api-respose.php

<?php
/**
 * Cache http response to store response data in cache once received success response.
 * This helps avoiding duplicate http requests. 
 * Also helpful in cases where we may have limited API requests rate. (i.e 25 requests per day)
 */

namespace WP_Local_Helper;

// Domain list which needs uncached response each time.
const EXCLUDE_CACHE_DOMAIN_LIST = [
	'example.org',
];
const CACHE_GROUP = 'local-helper';

/**
 * Maybe return respose from cache.
 *
 * @param false|array $response    A preemptive return value of an HTTP request.
 * @param array       $parsed_args HTTP request arguments.
 * @param string      $url         The request URL.
 *
 * @return false|array
 */
function maybe_return_cache_response( $response, $parsed_args, $url ) {

	$request_domain = wp_parse_url( $url, PHP_URL_HOST );
	$cache_key      = wp_hash( wp_json_encode( $parsed_args ) . $url  );
	$cache_response = wp_cache_get( $cache_key, CACHE_GROUP );

	if ( in_array( $request_domain, EXCLUDE_CACHE_DOMAIN_LIST ) || false === $cache_response ) {
		return $response;
	}

	// phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_error_log
	error_log( 'Return cache response. URL: ' . $url );

	return $cache_response;
}
add_filter('pre_http_request', __NAMESPACE__ . '\\maybe_return_cache_response', 10, 3 );

/**
 * Filters the HTTP API response immediately before the response is returned.
 *
 * @param array  $response    HTTP response.
 * @param array  $parsed_args HTTP request arguments.
 * @param string $url         The request URL.
 *
 * @return false|array
 */
function maybe_cache_response( $response, $parsed_args, $url ) {

	$request_domain = wp_parse_url( $url, PHP_URL_HOST );

	if (
		! in_array( $request_domain, EXCLUDE_CACHE_DOMAIN_LIST )
		 && ! empty( $response['response']['code'] )
		 && $response['response']['code'] === 200
	) {
		$cache_key = wp_hash( wp_json_encode( $parsed_args ) . $url  );
		wp_cache_set( $cache_key, $response, CACHE_GROUP );

		// phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_error_log
		error_log( 'Set cache response. URL: ' . $url );
	}

	return $response;
}
add_filter('http_response', __NAMESPACE__ . '\\maybe_cache_response', 10, 3 );