<?php
$myCurl = curl_init();
$data = array(
    'saleid'=>'326422184',
'location'=>'shop_browse',
'amount'=>'42',
'internal_search'=>'',
'csrf'=>'xxxxxxxxxxxxxxx'
);
curl_setopt( $myCurl, CURLOPT_URL, 'https://api.opskins.com/ICart/AddToCart/v1/' );
curl_setopt( $myCurl, CURLOPT_HTTPHEADER, array (
 'origin: https://opskins.com',
 'accept-encoding: gzip, deflate, br',
 'accept-language: ru-RU,ru;q=0.9,en-US;q=0.8,en;q=0.7',
 'user-agent: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.84 Safari/537.36',
 'content-type: application/x-www-form-urlencoded; charset=UTF-8',
 'accept: */*',
 'referer: https://opskins.com/?loc=shop_browse&app=730_2',
 'authority: api.opskins.com',
 'cookie: aaaaaaaaaaa=xxxxxxxxxxxx; xxxxxxxxxxxx=aaaaaaaaaaaaaaa; aaaaaaaa=xxxxxxxxxx; aaaaaaa=xxxx',
 ));
curl_setopt($myCurl,CURLOPT_ENCODING, '');

 curl_setopt($myCurl, CURLOPT_FOLLOWLOCATION, true);
 curl_setopt($myCurl, CURLOPT_COOKIEFILE, '');
 curl_setopt($myCurl, CURLOPT_HEADER, 0);
 curl_setopt($myCurl, CURLOPT_RETURNTRANSFER, 0);
curl_setopt($myCurl, CURLOPT_PROXYPORT, '8000');
curl_setopt($myCurl, CURLOPT_PROXY, '1.1.1.1');
curl_setopt($myCurl, CURLOPT_PROXYUSERPWD, 'xxxxxxxx:xxxxxxxx');
curl_setopt( $myCurl, CURLOPT_POST, 1 );
curl_setopt($myCurl, CURLOPT_POSTFIELDS, $data);
curl_setopt ($myCurl, CURLOPT_SSL_VERIFYPEER, 0);

if (curl_exec ( $myCurl ))
    echo 'OK!!';
else
    echo 'Error curl: ' . curl_error($myCurl);

curl_close($myCurl);
?>