Obtención de autorización

<?php
$end_point = "https://sandbox.decidir.com/services/t/1.1/Authorize.AuthorizeHttpSoap12Endpoint";
$wsdl = "https://sandbox.decidir.com/services/t/1.1/Authorize?wsdl";

$RequestKey=$_GET["rk"];
$AnswerKey=$_GET["pa"];

$headers = array(
  'http'=>array(
    'header'=>$http_header)
);
$contexto = stream_context_create($headers);


$array_de_datos = array(
    "Merchant"=>"12345678",
    "Security"=>"PRISMA RV82RVHO5T0O5CZUUTX2FLHU",
    "RequestKey"=>$RequestKey,
    "AnswerKey"=>$AnswerKey
);

$contexto = stream_context_create($headers);
$soap_client = new SoapClient($wsdl, array(
        'stream_context'=>$contexto,
    'location'=>$end_point,
    'encoding'=>"UTF-8",
    ));

var_dump($soap_client->GetAuthorizeAnswer($array_de_datos));

Ejemplo de Respuesta:

object(stdClass)#2 (5){
    ["StatusCode"]=> int(-1) ["StatusMessage"]=> string(8)
    "Aprobada" ["AuthorizationKey"]=> string(36)
    "a79ea4a6-3fdb-ec2d-1176-080957dab2f3" ["EncodingMethod"]=> string(3)
    "XML" ["Payload"]=> object(stdClass)#3 (2) {
        ["Answer"]=> object(stdClass)#4 (6) {
            ["FECHAHORA"]=> string(20) "2015-08-28T16:50:46Z"
            ["MONEDA"]=> string(0) ""
            ["NROTICKET"]=> string(3) "205"
            ["CODAUTORIZAción"]=> string(6) "165045"
            ["NROTARJETAVISIBLE"]=> string(16) "450799XXXXXX4905"
            ["CODBARRAS"]=> string(0) ""
        }
        ["Request"]=> object(stdClass)#5 (3) {
            ["NROCOMERCIO"]=> string(8) "12345678"
            ["NROOPERAción"]=> string(10) "9238742988"
            ["MONTO"]=> string(5) "50.00"
        }
    }
}