get subway stations and cities of Russia superjob API

.php

<?php

class CitySubway
{
    protected static $apiCitiesUrl = "https://api.superjob.ru/2.0/towns/";
    protected static $apiMetroListUrl = "https://api.superjob.ru/2.0/suggest/town/:id_town/metro/all/";

    public static function getAllCities()
    {
        $params = [
            'all' => 1,
            'genitive' => 1
        ];

        return self::getRequest(self::$apiCitiesUrl, $params);
    }

    public static function getCity($keyword)
    {
        $params = [
            'keyword' => $keyword,
            'genitive' => 1
        ];
        return self::getRequest(self::$apiCitiesUrl, $params);
    }

    public static function getSubways(string $cityName)
    {
        $cityId = self::getCityID($cityName);
        $url = preg_replace('~\:id_town~', $cityId, self::$apiMetroListUrl);

        return self::getRequest($url);
    }

    protected static function getRequest(string $url, array $params = [])
    {
        $queryString = '';

        foreach ($params as $name => $value) {
            if (empty($queryString)) $queryString .= '?';

            $queryString .= "&$name=$value";
        }

        $ch = curl_init();
        curl_setopt($ch, CURLOPT_URL, $url . $queryString);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
        $output = curl_exec($ch);
        curl_close($ch);

        return json_decode($output);
    }

    public static function getCityID($keyword)
    {
        $cityAr = array_shift(self::getCity($keyword)->objects);
        return $cityAr->id ?? NULL;
    }
}