Mastering PHP Payments with Omnipay

Complete after redirect

$gateway->completePurchase([
	'amount' => '10.00', 
	'currency' => 'USD', 
	'transactionId' => '1234' 
])->send();

When returning from an off - site gateway, you need to complete the purchase using the same options. Some gateways validate options to make sure the transaction hasn’t been messed with.