use CoinbaseWalletEnumCurrencyCode;
use CoinbaseWalletResourceTransaction;
use CoinbaseWalletValueMoney;

$transaction = Transaction::request([
    'amount'      => new Money(8, CurrencyCode::USD),
    'description' => 'Burrito'
]);

$client->createAccountTransaction($transaction);

<?php
require_once('vendor/autoload.php');

use CoinbaseWalletClient;
use CoinbaseWalletConfiguration;
use CoinbaseWalletEnumCurrencyCode;
use CoinbaseWalletResourceTransaction;
use CoinbaseWalletValueMoney;

$apiKey='xxxxxxx';
$apiSecret='xxxxxxx';
$configuration = Configuration::apiKey($apiKey, $apiSecret);
$client = Client::create($configuration);

$transaction = Transaction::request([
    'amount'      => new Money(8, CurrencyCode::USD),
    'description' => 'Burrito'
]);
$client->createAccountTransaction($transaction);
echo json_encode($client->decodeLastResponse());
?>