paypal_execute.php

<?php
/**
 * Created by PhpStorm.
 * User: Ricardo
 * Date: 24/03/2018
 * Time: 18:58
 */

require_once "paypal_config.php";

use PayPal\Api\Amount;
use PayPal\Api\Details;
use PayPal\Api\ExecutePayment;
use PayPal\Api\Payment;
use PayPal\Api\PaymentExecution;
use PayPal\Api\Transaction;

// Get payment object by passing paymentId
if(isset($_REQUEST['paymentID'])){
    $paymentId = $_REQUEST['paymentID'];
}

$payment = Payment::get($paymentId, $apiContext);
if(isset($_REQUEST['payerID'])){
    $payerId = $_REQUEST['payerID'];
}

// Execute payment with payer id
$execution = new PaymentExecution();
$execution->setPayerId($payerId);

try {
    // Execute payment
    $result = $payment->execute($execution, $apiContext);
    echo $result;
} catch (PayPal\Exception\PayPalConnectionException $ex) {
    echo $ex->getCode();
    echo $ex->getData();
    die($ex);
} catch (Exception $ex) {
    die($ex);
}