<?
$url = "https://www.rs-express.ru/payment/process";

$ch = curl_init();

curl_setopt($ch, CURLOPT_URL, $url);

curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);

curl_setopt($ch, CURLOPT_HEADER, true);

// указываем, что у нас POST запрос
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_HTTPHEADER, [
    'Host: www.rs-express.ru',
    'Connection: keep-alive',
    'Content-Length: 279',
    'Sec-Fetch-Mode: cors',
    'Origin: https://www.rs-express.ru',
    'X-CSRF-TOKEN: 8d32e716-799c-4592-9a30-d24e96daef5a',
    'User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.132 Safari/537.36',
    'Content-Type: application/json;charset=UTF-8',
    'Accept: application/json, text/plain, */*',
    'X-Requested-With: XMLHttpRequest',
    'DNT: 1',
    'Sec-Fetch-Site: same-origin',
    'Referer: https://www.rs-express.ru/payment/service/1315',
    'Accept-Encoding: gzip, deflate, br',
    'Accept-Language: ru-RU,ru;q=0.9,en-US;q=0.8,en;q=0.7,zh-TW;q=0.6,zh-CN;q=0.5,zh;q=0.4',
    'Cookie: _ym_uid=156863964424166821; _ym_d=1568639644; _ym_isad=2; __utmz=241797889.1568641855.2.2.utmcsr=yandex|utmccn=(organic)|utmcmd=organic; _ga=GA1.2.941699474.1568639644; _gid=GA1.2.210795219.1568642546; ASP.NET_SessionId=45F05E33D5BD304ABC1ED958A0BB3937.w2_8009; __utma=241797889.941699474.1568639644.1568655542.1568699285.4; __utmc=241797889; _ym_visorc_19284817=w; __utmt=1; __utmt_rsb=1; __utmb=241797889.30.10.1568699285',
]);
// добавляем переменные
curl_setopt($ch, CURLOPT_POSTFIELDS, '{"wid":"4","fields":{"id1":"410013776046488"},"cashSourceFields":{},"cashSource":"BANK","code":"","clientAccountId":null,"warning":null,"sum":{"income":1326,"commission":26,"outcome":1300},"sumProv":null,"sumProvCurrency":null,"flags":0,"failRegexConfirmed":false,"iframe":false}');

$output = curl_exec($ch);

curl_close($ch);

print_r($output);
?>