Getting "undefined variable" warning and "class not found" error when trying to use Paypal PHP SDK

Question

I want to integrate paypal payments to my site.

I tried integrating the paypal button form straight from paypal but there is a problem with it. The price of the product can be changed by easily inspecting the element and changing the price input.

I found out about the Paypal PHP SDK so I installed it via composer. The problem I'm having is when I want the user to pay for the product.

I copied and pasted the Create Payment method found here. But I'm getting an error:

Notice: Undefined variable: apiContext in C:\xampp\htdocs\paypal\index.php on line 62

Fatal error: Class 'ResultPrinter' not found in C:\xampp\htdocs\paypal\index.php on line 64

I know I'm getting this error because I haven't initialized this variable. I don't know where to create it and what this variable it must contain. How can I fully integrate this?

This is my full PHP code:

<?php

require 'vendor/autoload.php';
use PayPal\Api\Amount;
use PayPal\Api\Details;
use PayPal\Api\Item;
use PayPal\Api\ItemList;
use PayPal\Api\Payer;
use PayPal\Api\Payment;
use PayPal\Api\RedirectUrls;
use PayPal\Api\Transaction;

$payer = new Payer();
$payer->setPaymentMethod("paypal");

$item1 = new Item();
$item1->setName('Ground Coffee 40 oz')
    ->setCurrency('USD')
    ->setQuantity(1)
    ->setSku("123123") // Similar to `item_number` in Classic API
    ->setPrice(7.5);
$item2 = new Item();
$item2->setName('Granola bars')
    ->setCurrency('USD')
    ->setQuantity(5)
    ->setSku("321321") // Similar to `item_number` in Classic API
    ->setPrice(2);

$itemList = new ItemList();
$itemList->setItems(array($item1, $item2));

$details = new Details();
$details->setShipping(1.2)
    ->setTax(1.3)
    ->setSubtotal(17.50);

$amount = new Amount();
$amount->setCurrency("USD")
    ->setTotal(20)
    ->setDetails($details);

$transaction = new Transaction();
$transaction->setAmount($amount)
    ->setItemList($itemList)
    ->setDescription("Payment description")
    ->setInvoiceNumber(uniqid());

//I changed the base url and the return url's to mine.
$baseUrl = "http://www.localhost/paypal";
$redirectUrls = new RedirectUrls();
$redirectUrls->setReturnUrl("$baseUrl/ExecutePayment.php?success=true")
    ->setCancelUrl("$baseUrl/ExecutePayment.php?success=false");

$payment = new Payment();
$payment->setIntent("sale")
    ->setPayer($payer)
    ->setRedirectUrls($redirectUrls)
    ->setTransactions(array($transaction));

$request = clone $payment;

try {
    $payment->create($apiContext);
} catch (Exception $ex) {
    ResultPrinter::printError("Created Payment Using PayPal. Please visit the URL to Approve.", "Payment", null, $request, $ex);
    exit(1);
}

$approvalUrl = $payment->getApprovalLink();

ResultPrinter::printResult("Created Payment Using PayPal. Please visit the URL to Approve.", "Payment", "<a href='$approvalUrl' >$approvalUrl</a>", $request, $payment);

return $payment;

Answer 1

It looks like you've not defined $apiContext. I'm not totally familiar with this SDK but it looks like you can create one like so:

$apiContext = new \Paypal\Rest\ApiContext(
    new \PayPal\Auth\AuthTokenCredential(
        $clientId,
        $clientSecret
    )
);

reference

You will need to pass in your $clientId and $clientSecret that you have obtained from PayPal.