$ composer require halnique/php-slack-api
use Halnique\Slack;
$client = Slack\WebAPI\Client::create();
$apiTestResult = $client->call(Slack\WebAPI\Endpoints\HttpMethod::get(), 'api.test');
$authTestResult = $client->call(Slack\WebAPI\Endpoints\HttpMethod::post(), 'auth.test');
$usersLookupByEmailResult = $client->call(Slack\WebAPI\Endpoints\HttpMethod::get(), 'users.lookupByEmail', [
'email' => 'address@gmail.com',
]);