The merchant SDK can be used for integrating with the Express Checkout, Mass Pay, Web Payments Pro APIs.

PayPal's PHP Merchant SDK requires

• PHP 5.2 and above with curl/openssl extensions enabled

To use the SDK,

• Copy the config and lib folders into your project. Modify the config file sdk_config.ini to suit your needs.
• Make sure that the lib folder in your project is available in PHP's include path.
• Include the services\PayPalAPIInterfaceService\PayPalAPIInterfaceServiceService.php file in your code.
• Create a service wrapper object.
• Create a request object as per your project's needs. All the API request and response classes are available in services\PayPalAPIInterfaceService\PayPalAPIInterfaceServiceService.php
• Invoke the appropriate method on the service object.

For example,

require_once('services\PayPalAPIInterfaceService\PayPalAPIInterfaceServiceService.php');

$itemAmount = new BasicAmountType($currencyId, $amount);
$setECReqType = new SetExpressCheckoutRequestType();	
$setECReqType->SetExpressCheckoutRequestDetails = $setECReqDetails;

$setECReq = new SetExpressCheckoutReq();
$setECReq->SetExpressCheckoutRequest = $setECReqType;
......

$paypalService = new PayPalAPIInterfaceServiceService();
$setECResponse = $paypalService->SetExpressCheckout($setECReq);

$ack = strtoupper($setECResponse->Ack); 
if($ack == 'SUCCESS') {
	// Success
}  

The SDK provides multiple ways to authenticate your API call.

$paypalService = new PayPalAPIInterfaceServiceService();

// Use the default account (the first account) configured in sdk_config.ini
$response = $paypalService->SetExpressCheckout($setECReq);	

// Use a specific account configured in sdk_config.inig
$response = $paypalService->SetExpressCheckout($setECReq, 'jb-us-seller_api1.paypal.com');	
 
// Pass in a dynamically created API credential object
$cred = new PPCertificateCredential("username", "password", "path-to-pem-file");
$cred->setThirdPartyAuthorization(new PPTokenAuthorization("accessToken", "tokenSecret"));
$response = $paypalService->SetExpressCheckout($setECReq, $cred);	

Replace the API credential in config/sdk_config.ini . You can use the configuration file to configure

• (Multiple) API account credentials.
• Service endpoint and other HTTP connection parameters
• Logging

Please refer to the sample config file provided with this bundle.

*copy the contents in 'lib/service/' to one of the SDKs *add the service endpoint to 'config/sdk_config.ini', for the endpoints refer the list below

*The list below specifies endpoints for different services, in SANDBOX and PRODUCTION, with their property keys and end-point as property values.

------------------------------SANDBOX------------------------------

• Merchant/Button Manager Service (3 Token)
  service.EndPoint.PayPalAPI=https://api-3t.sandbox.paypal.com/2.0
  service.EndPoint.PayPalAPIAA=https://api-3t.sandbox.paypal.com/2.0

• Merchant/Button Manager Service (Certificate)
  service.EndPoint.PayPalAPI=https://api.sandbox.paypal.com/2.0
  service.EndPoint.PayPalAPIAA=https://api.sandbox.paypal.com/2.0

• AdaptiveAccounts Platform Service
  service.EndPoint.AdaptiveAccounts=https://svcs.sandbox.paypal.com/

• AdaptivePayments Platform Service
  service.EndPoint.AdaptivePayments=https://svcs.sandbox.paypal.com/

• Invoice Platform Service
  service.EndPoint.Invoice=https://svcs.sandbox.paypal.com/

• Permissions Platform Service
  service.EndPoint.Permissions=https://svcs.sandbox.paypal.com/

------------------------------PRODUCTION------------------------------

• Merchant/Button Manager Service (3 Token)
  service.EndPoint.PayPalAPI=https://api-3t.paypal.com/2.0
  service.EndPoint.PayPalAPIAA=https://api-3t.paypal.com/2.0

• Merchant/Button Manager Service (Certificate)
  service.EndPoint.PayPalAPI=https://api.paypal.com/2.0
  service.EndPoint.PayPalAPIAA=https://api.paypal.com/2.0

• AdaptiveAccounts Platform Service
  service.EndPoint.AdaptiveAccounts=https://svcs.paypal.com/

• AdaptivePayments Platform Service
  service.EndPoint.AdaptivePayments=https://svcs.paypal.com/

• Invoice Platform Service
  service.EndPoint.Invoice=https://svcs.paypal.com/

• Permissions Platform Service
  service.EndPoint.Permissions=https://svcs.paypal.com/

For additional information please refer to https://www.x.com/developers/paypal/documentation-tools/api

refer to the IPN-README in 'samples/IPN' directory

If you need help using the SDK, a new feature that you need or have a issue to report, please visit

https://github.com/paypal/merchant-sdk-php/issues

  OR

https://www.x.com/developers/paypal/forums/express-checkout