A WordPress REST Controller to pass-thru Google Analytics Data

class-wp-proxy.php

<?php
/**
 * @author   : Daan van den Bergh
 * @url      : https://daan.dev/how-to/bypass-ad-blockers-caos/
 * @copyright: (c) 2019 Daan van den Bergh
 * @license  : GPL2v2 or later
 */

class Analytics_Proxy extends WP_REST_Controller
{
    /** @var string $namespace */
    protected $namespace;

    /** @var string $rest_base */
    protected $rest_base;

    public function __construct()
    {
        $this->namespace = 'analytics/v1';
        $this->rest_base = 'proxy';
    }

    /**
     * This function makes sure the controller is reachable at wp-json/analytics/v1/proxy/collect
     */
    public function register_routes()
    {
        register_rest_route(
            $this->namespace,
            '/' . $this->rest_base . '/collect',
            array(
                array(
                    'methods'             => WP_REST_Server::READABLE,
                    'callback'            => array($this, 'send_data'),
                    'permission_callback' => array($this, 'send_data_permissions_check')
                ),
                'schema' => null,
            )
        );
    }

    /**
     * @param $request
     *
     * @return bool
     */
    public function send_data_permissions_check()
    {
        return true;
    }

    /**
     * The uip-parameter is added to the query, to keep the location data accurate.
     *
     * @param WP_REST_Request $request
     *
     * @return mixed|WP_Error|WP_REST_Response
     * @throws Exception
     */
    public function send_data($request)
    {
        $params  = $request->get_params();
        $ip      = $this->get_user_ip_address();
        $paramIp = array('uip' => $ip);
        $query   = '?' . http_build_query($params + $paramIp);
        $url     = 'https://www.google-analytics.com/collect' . $query;
        try {
            $response = wp_remote_get(
                $url
            );
        } catch (\Exception $error) {
            throw new Exception($error->getMessage());
        }

        return $response;
    }

    /**
     * Here we detect the User's IP address to make sure the location is still accurate.
     * @return string
     */
    private function get_user_ip_address()
    {
        if (!empty($_SERVER['HTTP_CLIENT_IP'])) {
            $ip = $_SERVER['HTTP_CLIENT_IP'];
        } elseif (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
            $ip = $_SERVER['HTTP_X_FORWARDED_FOR'];
        } else {
            $ip = $_SERVER['REMOTE_ADDR'];
        }

        /**
         * Some servers return multiple, comma-seapareted IP-addresses.
         * The correct one is usually the first one.
         */
        if (is_array(explode(',', $ip))) {
            $ip = explode(',', $ip);
            return $ip[0];
        }

        return $ip;
    }
}