Single Payment with PayPal Express Checkout API

doEC-one-time-simple-payment.php

require_once('services/PayPalApi/PayPalAPIInterfaceServiceService.php');

/* setup payment details */
orderTotal = new BasicAmountType( '-your-currency-code-', '-your-amount-');
$PaymentDetails= new PaymentDetailsType();
$PaymentDetails->OrderTotal = $orderTotal;

/* create DoExpressCheckout request details */
$DoECRequestDetails = new DoExpressCheckoutPaymentRequestDetailsType();
$DoECRequestDetails->PayerID = '-payer-id-from-get-EC-call;
$DoECRequestDetails->Token = '-token-from-set-EC-call-';
$DoECRequestDetails->PaymentDetails[0] = $PaymentDetails;

/* create DoExpressCheckoutPayment Request */
$DoECRequest = new DoExpressCheckoutPaymentRequestType();
$DoECRequest->DoExpressCheckoutPaymentRequestDetails = $DoECRequestDetails;
$DoECRequest->Version = '85.0';
$DoECReq = new DoExpressCheckoutPaymentReq();
$DoECReq->DoExpressCheckoutPaymentRequest = $DoECRequest;

/* Execute the API call */
$paypalService = new PayPalAPIInterfaceServiceService();
$DoECResponse = $paypalService->DoExpressCheckoutPayment($DoECReq);


/* check the return status */
if($DoECResponse->Ack =='Success')
{
  /* verify your payment info - before providing the item/resource to the consumer */
  $paymentStatus = $DoECResponse->DoExpressCheckoutPaymentResponseDetails->PaymentInfo->PaymentStatus;
}

getEC-one-time-simple-payment.php

require_once('services/PayPalApi/PayPalAPIInterfaceServiceService.php');

/* Create GetExpressCheckoutDetails request with token*/
$getExpressCheckoutDetailsRequest = new GetExpressCheckoutDetailsRequestType('-token-from-setEC-call-');
$getExpressCheckoutDetailsRequest->Version = 85.0;
$getExpressCheckoutReq = new GetExpressCheckoutDetailsReq();
$getExpressCheckoutReq->GetExpressCheckoutDetailsRequest = $getExpressCheckoutDetailsRequest;

/* execute the GetExpressCheckoutDetails API call */
$paypalService = new PayPalAPIInterfaceServiceService();
$getECResponse = $paypalService->GetExpressCheckoutDetails($getExpressCheckoutReq);

/* obtain the payerId */
if($getECResponse->Ack =='Success')
{
  $payerId = $getECResponse->GetExpressCheckoutDetailsResponseDetails->PayerInfo->PayerID;
  $amount = $getECResponse->GetExpressCheckoutDetailsResponseDetails->PaymentDetails->OrderTotal->value;
  /* TODO: Make sure amount and other information matches what you've asked for */

}

setEC-one-time-simple-payment.php

require_once('services/PayPalApi/PayPalAPIInterfaceServiceService.php');

/* Setup Payment Details */
$PaymentDetails= new PaymentDetailsType();
$PaymentDetails->OrderTotal =  new BasicAmountType('-your-currency-code-', '-your-amount-');
$PaymentDetails->PaymentAction = 'Sale';
$PaymentDetails->OrderDescription = '-your-payment-order-description-';

/* Setup Checkout request details */
$setECReqDetails = new SetExpressCheckoutRequestDetailsType();
$setECReqDetails->PaymentDetails = $PaymentDetails;
$setECReqDetails->CancelURL = 'http://-your-site-/-cancel-url-';
$setECReqDetails->ReturnURL = 'http://-your-site-/-return-url-';

/* create the SetExpressCheckoutRequest */
$setECReqType = new SetExpressCheckoutRequestType();
$setECReqType->SetExpressCheckoutRequestDetails = $setECReqDetails;
$setECReqType->Version = '85.0';
$setECReq = new SetExpressCheckoutReq();
$setECReq->SetExpressCheckoutRequest = $setECReqType;

/* execute the API call */
$paypalService = new PayPalAPIInterfaceServiceService();
$setECResponse = $paypalService->SetExpressCheckout($setECReq);

/* check the return status */
if($setECResponse->Ack =='Success')
{
  $token = $setECResponse->Token;
}