Zebra_cURL::get PHP Method

    public function get($urls, $callback = '')
    {
        // iterate through the list of URLs to process
        foreach ((array) $urls as $url) {
            // add each URL and associated properties to the "_requests" property
            $this->_requests[] = array('url' => $url, 'options' => array(CURLINFO_HEADER_OUT => 1, CURLOPT_HEADER => 1, CURLOPT_HTTPGET => 1, CURLOPT_NOBODY => 0, CURLOPT_BINARYTRANSFER => null, CURLOPT_CUSTOMREQUEST => null, CURLOPT_FILE => null, CURLOPT_POST => null, CURLOPT_POSTFIELDS => null), 'callback' => $callback, 'arguments' => array_slice(func_get_args(), 2));
        }
        // if we're just queuing requests for now, do not execute the next lines
        if ($this->_queue) {
            return;
        }
        // if we have to pause between batches of requests, process them sequentially, in batches
        if ($this->pause_interval > 0) {
            $this->_process_paused();
        } else {
            $this->_process();
        }
    }

 public static function do_sync()
 {
     global $wpdb;
     $debug_mode = defined('KIGO_DEBUG') && KIGO_DEBUG;
     // Do not log into New Relic, because this function is slow and we know why
     if (extension_loaded('newrelic')) {
         newrelic_ignore_transaction();
     }
     //Check that cron is "enabled" and that the secret is correct
     if (!defined('KIGO_CRON_SECRET') || !isset($_GET[self::GET_PARAM_CRON_SECRET]) || $_GET[self::GET_PARAM_CRON_SECRET] !== KIGO_CRON_SECRET) {
         self::log(array('message' => 'Missing/Invalid cron secret', 'info' => $_SERVER));
         self::handle_logs($debug_mode);
         exit;
     }
     // Ensure that no other cron will run concurrently by acquiring an advisory lock (at MySQL database)
     if (!$wpdb->get_var($wpdb->prepare('SELECT GET_LOCK(%s, 0)', self::ADV_LOCK_PROCESSING))) {
         self::log('Previous cron execution is not finished, could not acquire cron lock');
         self::handle_logs($debug_mode);
         exit;
     }
     $prevTimeTotal = microtime(true);
     if (is_multisite()) {
         require_once dirname(__FILE__) . '/ext/class-zebra-curl.php';
         // Change the default value of wp_is_large_network necessary if # of sites reach the 10000
         add_filter('wp_is_large_network', array('Kigo_Network_Cron', 'custom_wp_is_large_network'), 1, 3);
         // Initialize the list of sites
         $sites = wp_get_sites(array('limit' => self::CUSTOM_WP_IS_LARGE_NETWORK, 'deleted' => 0, 'archived' => 0));
         shuffle($sites);
         // Filter the sites, not to trigger a sync for site where the solution data have not been updated since X months
         self::filter_old_sites($sites);
         self::log(array('nb_sites' => count($sites)));
         //Do the Zebra cURL call (asynchronous calls)
         $curl = new Zebra_cURL();
         $curl->option(CURLOPT_TIMEOUT, self::CURL_TIMEOUT);
         $curl->threads = self::CURL_PARALLEL_CALLS;
         //Prepare URLs to be called
         $urls = array_map(array('Kigo_Network_Cron', 'generate_curl_urls'), $sites);
         $urls = array_filter($urls, function ($url) {
             return is_string($url);
         });
         $curl->get($urls, array('Kigo_Network_Cron', 'zebra_curl_callback'));
     } else {
         set_error_handler(array('Kigo_Network_Cron', 'php_error_handler'));
         // Add our custom handler for wp_die() because some functions die on error, and we don't want the script to die !
         add_filter('wp_die_ajax_handler', array('Kigo_Network_Cron', 'kigo_cron_wp_die_handler_filter'));
         $site_cron = new Kigo_Site_Cron();
         self::log($site_cron->sync_entities() ? true : $site_cron->_errors);
         restore_error_handler();
     }
     self::log(array('total_execution_time' => microtime(true) - $prevTimeTotal));
     if (!$wpdb->query($wpdb->prepare('SELECT RELEASE_LOCK(%s)', self::ADV_LOCK_PROCESSING))) {
         self::log('Could not release cron lock');
     }
     // Echo the logs in debug mode or send them by mail
     self::handle_logs($debug_mode);
     exit;
 }