Laravel - Paypal SDK Got Http response code 401

<?php

namespace App\\\\Http\\\\Controllers\\\\Site;

use Illuminate\\\\Http\\\\Request;
use App\\\\Http\\\\Controllers\\\\Controller;

use PayPal\\\\Api\\\\Address;
use PayPal\\\\Api\\\\BillingInfo;
use PayPal\\\\Api\\\\Cost;
use PayPal\\\\Api\\\\Currency;
use PayPal\\\\Api\\\\Invoice;
use PayPal\\\\Api\\\\InvoiceAddress;
use PayPal\\\\Api\\\\InvoiceItem;
use PayPal\\\\Api\\\\MerchantInfo;
use PayPal\\\\Api\\\\PaymentTerm;
use PayPal\\\\Api\\\\Phone;
use PayPal\\\\Api\\\\ShippingInfo;

use PayPal\\\\Auth\\\\OAuthTokenCredential;
use PayPal\\\\Rest\\\\ApiContext;

class PaypalController extends Controller
{
    private $_api_context;

    public function __construct()
    {
        /** PayPal api context **/
        $paypal_conf = \\\\Config::get(''paypal'');
        $this->_api_context = new ApiContext(new OAuthTokenCredential(
            $paypal_conf[''client_id''],
            $paypal_conf[''secret''])
        );
        $this->_api_context->setConfig($paypal_conf[''settings'']);
    }

    public function teste(){
        $invoice = new Invoice();
        // ### Invoice Info
        // Fill in all the information that is
        // required for invoice APIs
        $invoice
            ->setMerchantInfo(new MerchantInfo())
            ->setBillingInfo(array(new BillingInfo()))
            ->setNote("Medical Invoice 16 Jul, 2013 PST")
            ->setPaymentTerm(new PaymentTerm())
            ->setShippingInfo(new ShippingInfo());
        // ### Merchant Info
        // A resource representing merchant information that can be
        // used to identify merchant
        $invoice->getMerchantInfo()
            ->setEmail("jaypatel512-facilitator@hotmail.com")
            ->setFirstName("Dennis")
            ->setLastName("Doctor")
            ->setbusinessName("Medical Professionals, LLC")
            ->setPhone(new Phone())
            ->setAddress(new Address());
        $invoice->getMerchantInfo()->getPhone()
            ->setCountryCode("001")
            ->setNationalNumber("5032141716");
        // ### Address Information
        // The address used for creating the invoice
        $invoice->getMerchantInfo()->getAddress()
            ->setLine1("1234 Main St.")
            ->setCity("Portland")
            ->setState("OR")
            ->setPostalCode("97217")
            ->setCountryCode("US");
        // ### Billing Information
        // Set the email address for each billing
        $billing = $invoice->getBillingInfo();
        $billing[0]
            ->setEmail("example@example.com");
        $billing[0]->setBusinessName("Jay Inc")
            ->setAdditionalInfo("This is the billing Info")
            ->setAddress(new InvoiceAddress());
        $billing[0]->getAddress()
            ->setLine1("1234 Main St.")
            ->setCity("Portland")
            ->setState("OR")
            ->setPostalCode("97217")
            ->setCountryCode("US");
        // ### Items List
        // You could provide the list of all items for
        // detailed breakdown of invoice
        $items = array();
        $items[0] = new InvoiceItem();
        $items[0]
            ->setName("Sutures")
            ->setQuantity(100)
            ->setUnitPrice(new Currency());
        $items[0]->getUnitPrice()
            ->setCurrency("USD")
            ->setValue(5);
        // #### Tax Item
        // You could provide Tax information to each item.
        $tax = new \\\\PayPal\\\\Api\\\\Tax();
        $tax->setPercent(1)->setName("Local Tax on Sutures");
        $items[0]->setTax($tax);
        // Second Item
        $items[1] = new InvoiceItem();
        // Lets add some discount to this item.
        $item1discount = new Cost();
        $item1discount->setPercent("3");
        $items[1]
            ->setName("Injection")
            ->setQuantity(5)
            ->setDiscount($item1discount)
            ->setUnitPrice(new Currency());
        $items[1]->getUnitPrice()
            ->setCurrency("USD")
            ->setValue(5);
        // #### Tax Item
        // You could provide Tax information to each item.
        $tax2 = new \\\\PayPal\\\\Api\\\\Tax();
        $tax2->setPercent(3)->setName("Local Tax on Injection");
        $items[1]->setTax($tax2);
        $invoice->setItems($items);
        // #### Final Discount
        // You can add final discount to the invoice as shown below. You could either use "percent" or "value" when providing the discount
        $cost = new Cost();
        $cost->setPercent("2");
        $invoice->setDiscount($cost);
        $invoice->getPaymentTerm()
            ->setTermType("NET_45");
        // ### Shipping Information
        $invoice->getShippingInfo()
            ->setFirstName("Sally")
            ->setLastName("Patient")
            ->setBusinessName("Not applicable")
            ->setPhone(new Phone())
            ->setAddress(new InvoiceAddress());
        $invoice->getShippingInfo()->getPhone()
            ->setCountryCode("001")
            ->setNationalNumber("5039871234");
        $invoice->getShippingInfo()->getAddress()
            ->setLine1("1234 Main St.")
            ->setCity("Portland")
            ->setState("OR")
            ->setPostalCode("97217")
            ->setCountryCode("US");
        // ### Logo
        // You can set the logo in the invoice by providing the external URL pointing to a logo
        $invoice->setLogoUrl(''https://www.paypalobjects.com/webstatic/i/logo/rebrand/ppcom.svg'');
        // For Sample Purposes Only.
        $request = clone $invoice;
        try {
            // ### Create Invoice
            // Create an invoice by calling the invoice->create() method
            // with a valid ApiContext (See bootstrap.php for more on `ApiContext`)
            $invoice->create($this->_api_context);
        } catch (Exception $ex) {
            // NOTE: PLEASE DO NOT USE RESULTPRINTER CLASS IN YOUR ORIGINAL CODE. FOR SAMPLE ONLY
            ResultPrinter::printError("Create Invoice", "Invoice", null, $request, $ex);
            exit(1);
        }
        // NOTE: PLEASE DO NOT USE RESULTPRINTER CLASS IN YOUR ORIGINAL CODE. FOR SAMPLE ONLY
        ResultPrinter::printResult("Create Invoice", "Invoice", $invoice->getId(), $request, $invoice);
        return $invoice;

    }
}