code snippet that shows DocuSign Login API call using PHP client

LoginAPI.php

<?php

    require_once('./docusign-php-client/autoload.php');

    // DocuSign account credentials & Integrator Key
    $username = "[USERNAME]";
    $password = "[PASSWORD]";
    $integrator_key = "[INTEGRATOR_KEY]";

    // DocuSign environment we are using
    $host = "https://demo.docusign.net/restapi";

    // create a new DocuSign configuration and assign host and header(s)
    $config = new DocuSign\eSign\Configuration();
    $config->setHost($host);
    $config->addDefaultHeader("X-DocuSign-Authentication", "{\"Username\":\"" . $username . "\",\"Password\":\"" . $password . "\",\"IntegratorKey\":\"" . $integrator_key . "\"}");

    // instantiate a new docusign api client
    $apiClient = new DocuSign\eSign\ApiClient($config);

    // we will first make the Login() call which exists in the AuthenticationApi...
    $authenticationApi = new DocuSign\eSign\Api\AuthenticationApi($apiClient);

    // optional login parameters
    $options = new \DocuSign\eSign\Api\AuthenticationApi\LoginOptions();

    // call the login() API
    $loginInformation = $authenticationApi->login($options);

    // parse the login results
    if(isset($loginInformation) && count($loginInformation) > 0)
    {
        // note: defaulting to first account found, user might be a 
        // member of multiple accounts
        $loginAccount = $loginInformation->getLoginAccounts()[0];
        if(isset($loginInformation))
        {
            $accountId = $loginAccount->getAccountId();
            if(!empty($accountId))
            {
                echo "Account ID = $accountId\n";
            }
        }
    }

?>