Hello guys, Its really helpful for integration paypal in PHP to REST API.

To integrate it, first you have to download the PHP-paypal SDK below is the direct link
https://github.com/paypal/PayPal-PHP-SDK/releases

// 1. Autoload the SDK Package. This will include all the files and classes to your autoloader

<?php
require _DIR_ . '/PayPal-PHP-SDK/autoload.php';
use PayPal\Api\Amount;
use PayPal\Api\Details;
use PayPal\Api\Item;
use PayPal\Api\ItemList;
use PayPal\Api\CreditCard;
use PayPal\Api\Payer;
use PayPal\Api\Payment;
use PayPal\Api\FundingInstrument;
use PayPal\Api\Transaction;

// 2. Provide your Secret Key. Replace the given one with your app clientId, and Secret // https://developer.paypal.com/webapps/developer/applications/myapps

    $apiContext = new \PayPal\Rest\ApiContext(
        new \PayPal\Auth\OAuthTokenCredential(
            'AVv47dfPLzgZR4AJqOM4ch60p5vkJDekn0gg9o9QaFp123vl7Dl96Tcz-RQJRJ83m1gIF12Uvedd2gOxqGz6',     // ClientID
            'EJfrUYfyf8yoXfeqyswaMmyP54exKT5L2jjhJOjJHbRkmR4-TdPBvHzOkyffdy8HKhTLpQNMThTp5HVL1f'      // ClientSecret
        )
    );

if (!isset($_POST['paymentId'])){
        $response_Arr['message']='Please enter paymnet Id';
    }
    else
    {
        try {
            $payment = Payment::get($_POST['paymentId'], $apiContext);
          $obj = json_decode($payment); // $obj contains the All Transaction Information.Some of them,I have displayed Below.
          $trx_status=$obj-&gt;transactions[0]-&gt;related_resources[0]-&gt;sale-&gt;state;</p>

       if($trx_status == 'completed')
       {
         // Check user exist or not for payment


        }




      } catch (Exception $ex) {
      $response_Arr['message'] = $e-> getMessage();
      }

}

echo json_encode($response_Arr);
die();