$soap = new SoapClient("https://secure.przelewy24.pl/external/YOUR_MERCHANT_ID.wsdl"); $res= $soap->GetTransactionBySessionId('your_merchant_id','your_api_key','f3958fjsxndri');
//$res->result contains data about transaction,or object with empty field in case of error
if($res->error->errorCode){
    echo 'Something went wrong:'.$res->error->errorMessage;
} else {
    echo'Transaction:';
    $transaction = $res->result;
//data of transaction:$transaction->orderId,$transaction->amount,$transaction->date
}