Elgg\Http\Request::getFirstUrlSegment PHP Method

    public function getFirstUrlSegment()
    {
        $segments = $this->getUrlSegments();
        if ($segments) {
            return array_shift($segments);
        } else {
            return '';
        }
    }

/**
 * Set an initial context if using index.php front controller.
 *
 * @param Request $request Elgg HTTP request
 * @return void
 * @access private
 */
function _elgg_set_initial_context(\Elgg\Http\Request $request)
{
    // don't do this for *_handler.php, etc.
    if (basename($request->server->get('SCRIPT_FILENAME')) === 'index.php') {
        $context = $request->getFirstUrlSegment();
        if (!$context) {
            $context = 'main';
        }
        _elgg_services()->context->set($context);
    }
}