core-bundle/src/Controller/InitializeController.php
public function indexAction(): InitializeControllerResponse
    {
        @trigger_error('Custom entry points are deprecated and will no longer work in Contao 5.0.', E_USER_DEPRECATED);

        $masterRequest = $this->get('request_stack')->getMasterRequest();

        if (null === $masterRequest) {
            throw new \RuntimeException('The request stack did not contain a master request.');
        }

        $realRequest = Request::createFromGlobals();

        // Necessary to generate the correct base path
        foreach (['REQUEST_URI', 'SCRIPT_NAME', 'SCRIPT_FILENAME', 'PHP_SELF'] as $name) {
            $realRequest->server->set(
                $name,
                str_replace(TL_SCRIPT, 'index.php', $realRequest->server->get($name))
            );
        }

        $realRequest->attributes->replace($masterRequest->attributes->all());

        // Initialize the framework with the real request
        $this->get('request_stack')->push($realRequest);
        $this->get('contao.framework')->initialize();

        // Add the master request again. When Kernel::handle() is finished,
        // it will pop the current request, resulting in the real request being active.
        $this->get('request_stack')->push($masterRequest);

        return new InitializeControllerResponse('', 204);
    }
public function indexAction(): InitializeControllerResponse
    {
        @trigger_error('Custom entry points are deprecated and will no longer work in Contao 5.0.', E_USER_DEPRECATED);

        $masterRequest = $this->get('request_stack')->getMasterRequest();

        if (null === $masterRequest) {
            throw new \RuntimeException('The request stack did not contain a master request.');
        }

        $realRequest = Request::createFromGlobals();

        // Necessary to generate the correct base path
        foreach (['REQUEST_URI', 'SCRIPT_NAME', 'SCRIPT_FILENAME', 'PHP_SELF'] as $name) {
            $realRequest->server->set(
                $name,
                str_replace(TL_SCRIPT, 'index.php', $realRequest->server->get($name))
            );
        }

        $realRequest->attributes->replace($masterRequest->attributes->all());

        // Initialize the framework with the real request
        $this->get('request_stack')->push($realRequest);
        $this->get('contao.framework')->initialize();

        // Add the master request again. When Kernel::handle() is finished,
        // it will pop the current request, resulting in the real request being active.
        $this->get('request_stack')->push($masterRequest);

        return new InitializeControllerResponse('', 204);
    }
Initializes the Contao framework.

@throws \RuntimeException

@Route("/_contao/initialize", name="contao_initialize")