1. Go to this page and download the library: Download peterfox/bitpayclient library. Choose the download type require.
2. Extract the ZIP file and open the index.php.
3. Add this code to the index.php.
<?php
require_once('vendor/autoload.php');
/* Start to develop here. Best regards https://php-download.com/ */
peterfox / bitpayclient example snippets
$client = new BitPayClient('YOUR-API-KEY');
$invoiceResponse = $client->createInvoice(0.0001, 'BTC');