//Establedemos modo de cifrado
$modo = "aes-256-ecb";
//Ciframos el concepto encrypted de la transacción
$encrypted = openssl_encrypt($cadena, $modo, $merchantkey);
//Cifrar la cadena inicial en sha256 para el integrity check
$modo = "sha256"; 
$integrityCheck = hash($modo, $cadena);

//Concatenamos
$datos = 'encrypted=' . urlencode($encrypted) . '&integrityCheck=' . $integrityCheck . '&merchantId=' . $merchantid;


$url = 'https://checkout-stg.easypaymentgateway.com/EPGCheckout/rest/online/pay?' . $datos; 
			



$ch = curl_init($url);
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");
//curl_setopt($ch, CURLOPT_POSTFIELDS, $datos);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false); 
curl_setopt($ch, CURLOPT_HTTPHEADER, array(
    'Accept: application/xml')
);

curl_setopt($ch, CURLOPT_TIMEOUT, 6);
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 6);



//Lanzar Post

$result = curl_exec($ch);