Likely the multiple kernels approach could be a good option to solve this kind of project, but thinking now in Symfony 4 approach with environment variables, structure and kernel implementation, it could be improved.
Name-based Virtual Kernel
The term "Virtual Kernel" refers to the practice of running more than one application (such as api.example.com and admin.example.com) on a single project repository. Virtual kernels are "name-based", meaning that you have multiple kernel names running on each application. The fact that they are running on the same physical project repository is not apparent to the end user.
In short, each kernel name corresponds to one application.
Application-based Configuration
First, you'll need replicate the structure of one application for config, src, var directories and leave the root structure for shared bundles and configuration. It should look like this:
├── config/
│ ├── admin/
│ │ ├── packages/
│ │ ├── bundles.php
│ │ ├── routes.yaml
│ │ ├── security.yaml
│ │ └── services.yaml
│ ├── api/
│ ├── site/
│ ├── packages/
│ ├── bundles.php
├── src/
│ ├── Admin/
│ ├── Api/
│ ├── Site/
│ └── VirtualKernel.php
├── var/
│ ├── cache/
│ │ ├── admin/
│ │ │ └── dev/
│ │ │ └── prod/
│ │ ├── api/
│ │ └── site/
│ └── log/
Next, making use of the Kernel::$name property you can stand out the application to run with dedicated project files (var/cache/<name>/<env>/*):
<name><Env>DebugProjectContainer*<name><Env>DebugProjectContainerUrlGenerator*<name><Env>DebugProjectContainerUrlMatcher*
This will be the key of the performance as each application has by definition its own DI container, routes and configuration files. Here is a complete sample of the VirtualKernel class that supports the previous structure:
src/VirtualKernel.php
// WITHOUT NAMESPACE!
use Symfony\Component\HttpKernel\Kernel;
class VirtualKernel extends Kernel
{
use MicroKernelTrait;
private const CONFIG_EXTS = '.{php,xml,yaml,yml}';
public function __construct($environment, $debug, $name)
{
$this->name = $name;
parent::__construct($environment, $debug);
}
public function getCacheDir(): string
{
return $this->getProjectDir().'/var/cache/'.$this->name.'/'.$this->environment;
}
public function getLogDir(): string
{
return $this->getProjectDir().'/var/log/'.$this->name;
}
public function serialize()
{
return serialize(array($this->environment, $this->debug, $this->name));
}
public function unserialize($data)
{
[$environment, $debug, $name] = unserialize($data, array('allowed_classes' => false));
$this->__construct($environment, $debug, $name);
}
public function registerBundles(): iterable
{
$commonBundles = require $this->getProjectDir().'/config/bundles.php';
$kernelBundles = require $this->getProjectDir().'/config/'.$this->name.'/bundles.php';
foreach (array_merge($commonBundles, $kernelBundles) as $class => $envs) {
if (isset($envs['all']) || isset($envs[$this->environment])) {
yield new $class();
}
}
}
protected function configureContainer(ContainerBuilder $container, LoaderInterface $loader): void
{
$container->setParameter('container.dumper.inline_class_loader', true);
$this->doConfigureContainer($container, $loader);
$this->doConfigureContainer($container, $loader, $this->name);
}
protected function configureRoutes(RouteCollectionBuilder $routes): void
{
$this->doConfigureRoutes($routes);
$this->doConfigureRoutes($routes, $this->name);
}
private function doConfigureContainer(ContainerBuilder $container, LoaderInterface $loader, string $name = null): void
{
$confDir = $this->getProjectDir().'/config/'.$name;
if (is_dir($confDir.'/packages/')) {
$loader->load($confDir.'/packages/*'.self::CONFIG_EXTS, 'glob');
}
if (is_dir($confDir.'/packages/'.$this->environment)) {
$loader->load($confDir.'/packages/'.$this->environment.'/**/*'.self::CONFIG_EXTS, 'glob');
}
$loader->load($confDir.'/services'.self::CONFIG_EXTS, 'glob');
if (is_dir($confDir.'/'.$this->environment)) {
$loader->load($confDir.'/'.$this->environment.'/**/*'.self::CONFIG_EXTS, 'glob');
}
}
private function doConfigureRoutes(RouteCollectionBuilder $routes, string $name = null): void
{
$confDir = $this->getProjectDir().'/config/'.$name;
if (is_dir($confDir.'/routes/')) {
$routes->import($confDir.'/routes/*'.self::CONFIG_EXTS, '/', 'glob');
}
if (is_dir($confDir.'/routes/'.$this->environment)) {
$routes->import($confDir.'/routes/'.$this->environment.'/**/*'.self::CONFIG_EXTS, '/', 'glob');
}
$routes->import($confDir.'/routes'.self::CONFIG_EXTS, '/', 'glob');
}
}
Now your \VirtualKernel class requires an extra argument (name) that defines the application to load. In order for the autoloader to find your new \VirtualKernel class, make sure add it to composer.json autoload section:
"autoload": {
"classmap": [
"src/VirtualKernel.php"
],
"psr-4": {
"Admin\\": "src/Admin/",
"Api\\": "src/Api/",
"Site\\": "src/Site/"
}
},
Then, run composer dump-autoload to dump the new autoload config.
Keeping one entry point for all applications
├── public/
│ └── index.php
Following the same filosofy of Symfony 4, whereas environment variables decides which development environment and debug mode should be used to run your application, you could add a new APP_NAME environment variable to set the application to execute:
public/index.php
// ...
$kernel = new \VirtualKernel(getenv('APP_ENV'), getenv('APP_DEBUG'), getenv('APP_NAME'));
// ...
For now, you can play with it by using PHP's built-in Web server, prefixing the new application environment variable:
$ APP_NAME=site php -S 127.0.0.1:8000 -t public
$ APP_NAME=admin php -S 127.0.0.1:8001 -t public
$ APP_NAME=api php -S 127.0.0.1:8002 -t public
Executing commands per application
├── bin/
│ └── console.php
Add a new console option --kernel to be able to run commands from different applications:
bin/console
// ...
$name = $input->getParameterOption(['--kernel', '-k'], getenv('APP_NAME') ?: 'site');
//...
$kernel = new \VirtualKernel($env, $debug, $name);
$application = new Application($kernel);
$application
->getDefinition()
->addOption(new InputOption('--kernel', '-k', InputOption::VALUE_REQUIRED, 'The kernel name', $kernel->getName()))
;
$application->run($input);
Later, use this option to run any command different to default one (site).
$ bin/console about -k=api
Or if you prefer, use environment variables:
$ export APP_NAME=api
$ bin/console about # api application
$ bin/console debug:router # api application
$
$ APP_NAME=admin bin/console debug:router # admin application
Also you can configure the default APP_NAME environment variable in the .env file.
Running tests per application
├── tests/
│ ├── Admin/
│ │ └── AdminWebTestCase.php
│ ├── Api/
│ ├── Site/
The tests directory is pretty similar to the src directory, just update the composer.json to map each directory tests/<Name>/ with its PSR-4 namespace:
"autoload-dev": {
"psr-4": {
"Admin\\Tests\\": "tests/Admin/",
"Api\\Tests\\": "tests/Api/",
"Site\\Tests\\": "tests/Site/"
}
},
Again, run composer dump-autoload to re-generate the autoload config.
Here, you might need create a <Name>WebTestCase class per application in order to execute all tests together:
test/Admin/AdminWebTestCase
namespace Admin\Tests;
use Symfony\Bundle\FrameworkBundle\Test\WebTestCase;
abstract class AdminWebTestCase extends WebTestCase
{
protected static function createKernel(array $options = array())
{
return new \VirtualKernel(
isset($options['environment']) ? $options['environment'] : 'test',
isset($options['debug']) ? $options['debug'] : true,
'admin'
);
}
}
Later, extends from AdminWebTestCase to test admin.company.com application (Do the same for another ones).
Production and vhosts
Set the environment variable APP_NAME for each vhost config in your production server and development machine:
<VirtualHost company.com:80>
SetEnv APP_NAME site
# ...
</VirtualHost>
<VirtualHost admin.company.com:80>
SetEnv APP_NAME admin
# ...
</VirtualHost>
<VirtualHost api.company.com:80>
SetEnv APP_NAME api
# ...
</VirtualHost>
Adding more applications to the project
With three simple steps you should be able to add new vKernel/applications to the current project:
- Add to
config, src and tests directories a new folder with the <name> of the application and its content.
- Add to
config/<name>/ dir at least the bundles.php file.
- Add to
composer.json autoload/autoload-dev sections the new PSR-4 namespaces for src/<Name>/ and tests/<Name> directories and update the autoload config file.
Check the new application running bin/console about -k=<name>.
Final directory structure:
├── bin/
│ └── console.php
├── config/
│ ├── admin/
│ │ ├── packages/
│ │ ├── bundles.php
│ │ ├── routes.yaml
│ │ ├── security.yaml
│ │ └── services.yaml
│ ├── api/
│ ├── site/
│ ├── packages/
│ ├── bundles.php
├── public/
│ └── index.php
├── src/
│ ├── Admin/
│ ├── Api/
│ ├── Site/
│ └── VirtualKernel.php
├── tests/
│ ├── Admin/
│ │ └── AdminWebTestCase.php
│ ├── Api/
│ ├── Site/
├── var/
│ ├── cache/
│ │ ├── admin/
│ │ │ └── dev/
│ │ │ └── prod/
│ │ ├── api/
│ │ └── site/
│ └── log/
├── .env
├── composer.json
Unlike multiple kernel files approach, this version reduces a lot of code duplication and files; just one kernel, index.php and console for all applications, thanks to environment variables and virtual kernel class.
Example based-on Symfony 4 skeleton: https://github.com/yceruto/symfony-skeleton-vkernel
Inspired in https://symfony.com/doc/current/configuration/multiple_kernels.html
