This repo is mainly based on https://nitropack.io/download/plugin/nitropack-php-sdk-limited-support with some areas tidied up and refactored to allow composer installation.
composer require macroman/nitropack-api
use NitroPack\NitroPack;
use NitroPack\PurgeType;
// Initialize API
$nitro = new NitroPack('site_id', 'secret');
// Clear entire cache
$nitro->purgeCache();
// Clear specific URL
$nitro->purgeCache('https://example.com/');
// Clear tagged pages
$nitro->purgeCache(null, 'tag-name');
// Clear cache leaving a reason (shows in WordPress settings page)
$nitro->purgeCache(null, null, PurgeType::COMPLETE, 'This is my reason');
// Add a tag to a URL
$nitro->tagUrl('https://example.com/', 'tag-name');
// Enable/disable compression
$nitro->enableCompression();
$nitro->disableCompression();
More functionality available, but not documented. Look at NitroPack\NitroPack.php for more information.