private static function loadUserAgents($filterBy = [])
    {
        $filterBy = self::validateFilter($filterBy);

        $agentDetails = self::getAgentDetails();
        $agentStrings = [];

        for ($i = 0; $i < count($agentDetails); $i++) {
            foreach ($filterBy as $key => $value) {
                if (!isset($agentDetails[$i][$key]) || !self::inFilter($agentDetails[$i][$key], $value)) {
                    continue 2;
                }
            }
            $agentStrings[] = $agentDetails[$i]['agent_string'];
        }

        return array_values($agentStrings);
    }