require_once('/path/to/SwaggerClient-php/vendor/autoload.php');

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

// Configure API key authorization: api_key
$config = CaelumPhpClient\Configuration::getDefaultConfiguration()->setApiKey('x-api-key', 'YOUR_API_KEY');
// Uncomment below to setup prefix (e.g. Bearer) for API key, if needed
// $config = CaelumPhpClient\Configuration::getDefaultConfiguration()->setApiKeyPrefix('x-api-key', 'Bearer');

$apiInstance = new CaelumPhpClient\Api\AuthApi(
    // If you want use custom http client, pass your client which implements `GuzzleHttp\ClientInterface`.
    // This is optional, `GuzzleHttp\Client` will be used as default.
    new GuzzleHttp\Client(),
    $config
);
$body = new \CaelumPhpClient\Model\SignInModel(); // \CaelumPhpClient\Model\SignInModel | 

try {
    $result = $apiInstance->apiV1AuthSigninPost($body);
    print_r($result);
} catch (Exception $e) {
    echo 'Exception when calling AuthApi->apiV1AuthSigninPost: ', $e->getMessage(), PHP_EOL;
}
?>