The Front Controller ¶

Up until now, our application is simplistic as there is only one page. To spice things up a little bit, let's go crazy and add another page that says goodbye:

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// framework/bye.php
require_once __DIR__.'/vendor/autoload.php';

use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;

$request = Request::createFromGlobals();

$response = new Response('Goodbye!');
$response->send();

As you can see for yourself, much of the code is exactly the same as the one we have written for the first page. Let's extract the common code that we can share between all our pages. Code sharing sounds like a good plan to create our first "real" framework!

The PHP way of doing the refactoring would probably be the creation of an include file:

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// framework/init.php
require_once __DIR__.'/vendor/autoload.php';

use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;

$request = Request::createFromGlobals();
$response = new Response();

Let's see it in action:

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// framework/index.php
require_once __DIR__.'/init.php';

$name = $request->query->get('name', 'World');

$response->setContent(sprintf('Hello %s', htmlspecialchars($name, ENT_QUOTES, 'UTF-8')));
$response->send();

And for the "Goodbye" page:

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// framework/bye.php
require_once __DIR__.'/init.php';

$response->setContent('Goodbye!');
$response->send();

We have indeed moved most of the shared code into a central place, but it does not feel like a good abstraction, does it? We still have the send() method for all pages, our pages do not look like templates and we are still not able to test this code properly.

Moreover, adding a new page means that we need to create a new PHP script, the name of which is exposed to the end user via the URL (http://127.0.0.1:4321/bye.php). There is a direct mapping between the PHP script name and the client URL. This is because the dispatching of the request is done by the web server directly. It might be a good idea to move this dispatching to our code for better flexibility. This can be achieved by routing all client requests to a single PHP script.

Such a script might look like the following:

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// framework/front.php
require_once __DIR__.'/vendor/autoload.php';

use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;

$request = Request::createFromGlobals();
$response = new Response();

$map = [
    '/hello' => __DIR__.'/hello.php',
    '/bye'   => __DIR__.'/bye.php',
];

$path = $request->getPathInfo();
if (isset($map[$path])) {
    require $map[$path];
} else {
    $response->setStatusCode(404);
    $response->setContent('Not Found');
}

$response->send();

And here is for instance the new hello.php script:

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// framework/hello.php
$name = $request->query->get('name', 'World');
$response->setContent(sprintf('Hello %s', htmlspecialchars($name, ENT_QUOTES, 'UTF-8')));

In the front.php script, $map associates URL paths with their corresponding PHP script paths.

As a bonus, if the client asks for a path that is not defined in the URL map, we return a custom 404 page. You are now in control of your website.

To access a page, you must now use the front.php script:

• http://127.0.0.1:4321/front.php/hello?name=Fabien
  http://127.0.0.1:4321/front.php/hello?name=ファビアン
• http://127.0.0.1:4321/front.php/bye
  http://127.0.0.1:4321/front.php/さようなら

/hello and /bye are the page paths.

The trick is the usage of the Request::getPathInfo() method which returns the path of the Request by removing the front controller script name including its sub-directories (only if needed -- see above tip).

Now that the web server always accesses the same script (front.php) for all pages, we can secure the code further by moving all other PHP files outside of the web root directory:

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example.com
├── composer.json
├── composer.lock
├── src
│   └── pages
│       ├── hello.php
│       └── bye.php
├── vendor
│   └── autoload.php
└── web
    └── front.php

Now, configure your web server root directory to point to web/ and all other files will no longer be accessible from the client.

To test your changes in a browser (http://localhost:4321/hello?name=Fabien), run the Symfony Local Web Server:

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$ symfony server:start --port=4321 --passthru=front.php

The last thing that is repeated in each page is the call to setContent(). We can convert all pages to "templates" by echoing the content and calling the setContent() directly from the front controller script:

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// example.com/web/front.php

// ...

$path = $request->getPathInfo();
if (isset($map[$path])) {
    ob_start();
    include $map[$path];
    $response->setContent(ob_get_clean());
} else {
    $response->setStatusCode(404);
    $response->setContent('Not Found');
}

// ...

And the hello.php script can now be converted to a template:

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<!-- example.com/src/pages/hello.php -->
<?php $name = $request->query->get('name', 'World') ?>

Hello <?= htmlspecialchars($name, ENT_QUOTES, 'UTF-8') ?>

We have the first version of our framework:

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// example.com/web/front.php
require_once __DIR__.'/../vendor/autoload.php';

use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;

$request = Request::createFromGlobals();
$response = new Response();

$map = [
    '/hello' => __DIR__.'/../src/pages/hello.php',
    '/bye'   => __DIR__.'/../src/pages/bye.php',
];

$path = $request->getPathInfo();
if (isset($map[$path])) {
    ob_start();
    include $map[$path];
    $response->setContent(ob_get_clean());
} else {
    $response->setStatusCode(404);
    $response->setContent('Not Found');
}

$response->send();

Adding a new page is a two-step process: add an entry in the map and create a PHP template in src/pages/. From a template, get the Request data via the $request variable and tweak the Response headers via the $response variable.