The Front Controller
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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.
Tip
Exposing a single PHP script to the end user is a design pattern called the "front controller".
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/bye
/hello
and /bye
are the page paths.
Tip
Most web servers like Apache or nginx are able to rewrite the incoming URLs
and remove the front controller script so that your users will be able to
type http://127.0.0.1:4321/hello?name=Fabien
, which looks much better.
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).
Tip
You don't even need to set up a web server to test the code. Instead,
replace the $request = Request::createFromGlobals();
call to something
like $request = Request::create('/hello?name=Fabien');
where the
argument is the URL path you want to simulate.
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:
1
$ symfony server:start --port=4321 --passthru=front.php
Note
For this new structure to work, you will have to adjust some paths in various PHP files; the changes are left as an exercise for the reader.
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.
Note
If you decide to stop here, you can probably enhance your framework by extracting the URL map to a configuration file.