A heierarchical resource-oriented micro-framework built on nested closures instead of route-based callbacks

v1.7.1 2021-05-28 16:07 UTC


Bullet is a resource-oriented micro PHP framework built around HTTP URIs. Bullet takes a unique functional-style approach to URL routing by parsing each path part independently and one at a time using nested closures. The path part callbacks are nested to produce different responses and to follow and execute deeper paths as paths and parameters are matched.

Build Status


Bullet becomes an active project again. Currently there's a changing of the guard. Feel free to further use and contribute to the framework.


  • PHP 5.6+ (PHP 7.1 recommended)
  • Composer for all package management and autoloading (may require command-line access)


  • Apps are built around HTTP URIs and defined paths, not forced MVC (but MVC-style separation of concerns is still highly recommenended and encouraged)
  • Bullet handles one segment of the path at a time, and executes the callback for that path segment before proceesing to the next segment (path callbacks are executed from left to right, until the entire path is consumed).
  • If the entire path cannot be consumed, a 404 error will be returned (note that some callbacks may have been executed before Bullet can know this due to the nature of callbacks and closures). Example: path /events/45/edit may return a 404 because there is no edit path callback, but paths events and 45 would have already been executed before Bullet can know to return a 404. This is why all your primary logic should be contained in get, post, or other method callbacks or in the model layer (and not in the bare path handlers).
  • If the path can be fully consumed, and HTTP method handlers are present in the path but none are matched, a 405 "Method Not Allowed" response will be returned.
  • If the path can be fully consumed, and format handlers are present in the path but none are matched, a 406 "Not Acceptable" response will be returned.


  • Super flexible routing. Because of the way the routing callbacks are nested, Bullet's routing system is one of the most flexible of any other PHP framework or library. You can build any URL you want and respond to any HTTP method on that URL. Routes are not restricted to specific patterns or URL formats, and do not require a controller with specific method names to respond to specific HTTP methods. You can nest routes as many levels deep as you want to expose nested resources like posts/42/comments/943/edit with a level of ease not found in most other routing libraries or frameworks.

  • Reduced code duplication (DRY). Bullet takes full advantage of its nested closure routing system to reduce a lot of typical code duplication required in most other frameworks. In a typical MVC framework controller, some code has to be duplicated across methods that perform CRUD operations to run ACL checks and load required resources like a Post object to view, edit or delete. With Bullet's nested closure style, this code can be written just once in a path or param callback, and then you can use the loaded object in subsequent path, param, or HTTP method handlers. This eliminates the need for "before" hooks and filters, because you can just run the checks and load objects you need before you define other nested paths and use them when required.

Installing with Composer

Use the basic usage guide, or follow the steps below:

Setup your composer.json file at the root of your project

    "require": {
        "vlucas/bulletphp": "~1.7"

Install Composer

curl -s http://getcomposer.org/installer | php

Install Dependencies (will download Bullet)

php composer.phar install

Create index.php (use the minimal example below to get started)

require __DIR__ . '/vendor/autoload.php';

/* Simply build the application around your URLs */
$app = new Bullet\App();

$app->path('/', function($request) {
    return "Hello World!";
$app->path('/foo', function($request) {
    return "Bar!";

/* Run the app! (takes $method, $url or Bullet\Request object)
 * run() always return a \Bullet\Response object (or throw an exception) */

$app->run(new Bullet\Request())->send();

This application can be placed into your server's document root. (Make sure it is correctly configured to serve php applications.) If index.php is in the document root on your local host, the application may be called like this:




If you're using Apache, use an .htaccess file to beautify the URLs. You need mod_rewrite to be installed and enabled.

<IfModule mod_rewrite.c>
  RewriteEngine On

  # Reroute any incoming requestst that is not an existing directory or file
  RewriteCond %{REQUEST_FILENAME} !-d
  RewriteCond %{REQUEST_FILENAME} !-f
  RewriteRule ^(.*)$ index.php?u=$1 [L,QSA,B]

With this file in place Apache will pass the request URI to index.php using the $_GET['u'] parameter. This works in subdirectories as expected i.e. you don't have to explicitly take care of removing the path prefix e.g. if you use mod_userdir, or just install a Bullet application under an existing web app to serve an API or simple, quick dynamic pages. Now your application will answer to these pretty urls:




NGinx also has a rewrite command, and can be used to the same end:

server {
    # ...
    location / {
        # ...
        rewrite ^/(.*)$ /index.php?u=/$1;
        try_files $uri $uri/ =404;
        # ...
    # ...

If the Bullet application is inside a subdirectory, you need to modify the rewrite line to serve it correctly:

server {
    # ...
    location / {
        rewrite ^/bulletapp/(.*)$ /bulletapp/index.php?u=/$1;
        try_files $uri $uri/ =404;
    # ...

Note that if you need to serve images, stylesheets, or javascript too, you need to add a location for the static root directory without the reqrite to avoid passing those URLs to index.php.

View it in your browser!


Bullet is not your typical PHP micro framework. Instead of defining a full path pattern or a typical URL route with a callback and parameters mapped to a REST method (GET, POST, etc.), Bullet parses only ONE URL segment at a time, and only has two methods for working with paths: path and param. As you may have guessed, path is for static path names like "blog" or "events" that won't change, and param is for variable path segments that need to be captured and used, like "42" or "my-post-title". You can then respond to paths using nested HTTP method callbacks that contain all the logic for the action you want to perform.

This type of unique callback nesting eliminates repetitive code for loading records, checking authentication, and performing other setup work found in typical MVC frameworks or other microframeworks where each callback or action is in a separate scope or controller method.

$app = new Bullet\App(array(
    'template.cfg' => array('path' => __DIR__ . '/templates')

// 'blog' subdirectory
$app->path('blog', function($request) use($app) {

    $blog = somehowGetBlogMapper(); // Your ORM or other methods here

    // 'posts' subdirectory in 'blog' ('blog/posts')
    $app->path('posts', function() use($app, $blog) {

        // Load posts once for handling by GET/POST/DELETE below
        $posts = $blog->allPosts(); // Your ORM or other methods here

        // Handle GET on this path
        $app->get(function() use($posts) {
            // Display all $posts
            return $app->template('posts/index', compact('posts'));

        // Handle POST on this path
        $app->post(function() use($posts) {
            // Create new post
            $post = new Post($request->post());
            return $this->response($post->toJSON(), 201);

        // Handle DELETE on this path
        $app->delete(function() use($posts) {
            // Delete entire posts collection
            return 200;


// Run the app and echo the response
echo $app->run("GET", "blog/posts");

Capturing Path Parameters

Perhaps the most compelling use of URL routing is to capture path segments and use them as parameters to fetch items from a database, like /posts/42 and /posts/42/edit. Bullet has a special param handler for this that takes two arguments: a test callback that validates the parameter type for use, and and a Closure callback. If the test callback returns boolean false, the closure is never executed, and the next path segment or param is tested. If it returns boolean true, the captured parameter is passed to the Closure as the second argument.

Just like regular paths, HTTP method handlers can be nested inside param callbacks, as well as other paths, more parameters, etc.

$app = new Bullet\App(array(
    'template.cfg' => array('path' => __DIR__ . '/templates')
$app->path('posts', function($request) use($app) {
    // Integer path segment, like 'posts/42'
    $app->param('int', function($request, $id) use($app) {
        $app->get(function($request) use($id) {
            // View post
            return 'view_' . $id;
        $app->put(function($request) use($id) {
            // Update resource
            return 'update_' . $id;
        $app->delete(function($request) use($id) {
            // Delete resource
            return 'delete_' . $id;
    // All printable characters except space
    $app->param('ctype_graph', function($request, $slug) use($app) {
        return $slug; // 'my-post-title'

// Results of above code
echo $app->run('GET',   '/posts/42'); // 'view_42'
echo $app->run('PUT',   '/posts/42'); // 'update_42'
echo $app->run('DELETE', '/posts/42'); // 'delete_42'

echo $app->run('DELETE', '/posts/my-post-title'); // 'my-post-title'

Returning JSON (Useful for PHP JSON APIs)

Bullet has built-in support for returning JSON responses. If you return an array from a route handler (callback), Bullet will assume the response is JSON and automatically json_encode the array and return the HTTP response with the appropriate Content-Type: application/json header.

$app->path('/', function($request) use($app) {
    $app->get(function($request) use($app) {
        // Links to available resources for the API
        $data = array(
            '_links' => array(
                'restaurants' => array(
                    'title' => 'Restaurants',
                    'href' => $app->url('restaurants')
                'events' => array(
                    'title' => 'Events',
                    'href' => $app->url('events')

        // Format responders
        $app->format('json', function($request), use($app, $data) {
            return $data; // Auto json_encode on arrays for JSON requests
        $app->format('xml', function($request), use($app, $data) {
            return custom_function_convert_array_to_xml($data);
        $app->format('html', function($request), use($app, $data) {
            return $app->template('index', array('links' => $data));

HTTP Response Bullet Sends:


Bullet Response Types

There are many possible values you can return from a route handler in Bullet to produce a valid HTTP response. Most types can be either returned directly, or wrapped in the $app->response() helper for additional customization.


$app = new Bullet\App();
$app->path('/', function($request) use($app) {
    return "Hello World";
$app->path('/', function($request) use($app) {
    return $app->response("Hello Error!", 500);

Strings result in a 200 OK response with a body containing the returned string. If you want to return a quick string response with a different HTTP status code, use the $app->response() helper.


$app = new Bullet\App();
$app->path('/', function($request) use($app) {
    return true;
$app->path('notfound', function($request) use($app) {
    return false;

Boolean false results in a 404 "Not Found" HTTP response, and boolean true results in a 200 "OK" HTTP response.


$app = new Bullet\App();
$app->path('teapot', function($request) use($app) {
    return 418;

Integers are mapped to their corresponding HTTP status code. In this example, a 418 "I'm a Teapot" HTTP response would be sent.


$app = new Bullet\App();
$app->path('foo', function($request) use($app) {
    return array('foo' => 'bar');
$app->path('bar', function($request) use($app) {
    return $app->response(array('bar' => 'baz'), 201);

Arrays are automatically passed through json_encode and the appropriate Content-Type: application/json HTTP response header is sent.


// Configure template path with constructor
$app = new Bullet\App(array(
    'template.cfg' => array('path' => __DIR__ . '/templates')

// Routes
$app->path('foo', function($request) use($app) {
    return $app->template('foo');
$app->path('bar', function($request) use($app) {
    return $app->template('bar', array('bar' => 'baz'), 201);

The $app->template() helper returns an instance of Bullet\View\Template that is lazy-rendered on __toString when the HTTP response is sent. The first argument is a template name, and the second (optional) argument is an array of parameters to pass to the template for use.

Serving large responses

Bullet works by wrapping every possible reponse with a Response object. This would normally mean that the entire request must be known (~be in memory) when you construct a new Response (either explicitly, or trusting Bullet to construct one for you).

This would be bad news for those serving large files or contents of big database tables or collections, since everything would have to be loaded into memory.

Here comes \Bullet\Response\Chunked for the rescue.

This response type requires some kind of iterable type. It works with regular arrays or array-like objects, but most importatnly, it works with generator functions too. Here's an example (database functions are purely fictional):

$app->path('foo', function($request) use($app) {
    $g = function () {
        $cursor = new ExampleDatabaseQuery("select * from giant_table");
        foreach ($cursor as $row) {
            yield example_format_db_row($row);
    return new \Bullet\Response\Chunked($g());

The $g variable will contain a Closure that uses yield to fetch, process, and return data from a big dataset, using only a fraction of the memory needed to store all the rows at once.

This results in a HTTP chunked response. See https://tools.ietf.org/html/rfc7230#section-4.1 for the technical details.

HTTP Server Sent Events

Server sent events are one way to open up a persistent channel to a web server, and receive notifications. This can be used to implement a simple webchat for example.

This standard is part of HTML5, see https://html.spec.whatwg.org/multipage/server-sent-events.html#server-sent-events for details.

The example below show a simple application using the fictional send_message and receive_message functions for communications. These can be implemented over various message queues, or simple named pipes.

$app->path('sendmsg', function($request) {
    $this->post(function($request) {
        $data = $request->postParam('message');
        return 201;

$app->path('readmsgs', function($request) {
    $this->get(function($request) {
        $g = function () {
            while (true) {
                $data = receive_message();
                yield [
                    'event' => 'message',
                    'data'  => $data
        \Bullet\Response\Sse::cleanupOb(); // Remove any output buffering
        return new \Bullet\Response\Sse($g());

The SSE response uses chunked encoding, contrary to the recommendation in the standard. We can do this, since we tailoe out chunks to be exactly message-sized.

This will not confuse upstream servers when they see no chunked encoding, AND no Content-Length header field, and might try to "fix" this by either reading the entire response, or doing the chunking on their own.

PHP's output buffering can also interfere with messaging, hence the call to \Bullet\Response\Sse::cleanupOb(). This method flushes and ends every level of output buffering that might present before sending the response.

The SSE response automatically sends the X-Accel-Buffering: no header to prevent the server from buffering the messages.

Nested Requests (HMVC style code re-use)

Since you explicitly return values from Bullet routes instead of sending output directly, nested/sub requests are straightforward and easy. All route handlers will return Bullet\Response instances (even if they return a raw string or other data type, they are wrapped in a response object by the run method), and they can be composed to form a single HTTP response.

$app = new Bullet\App();
$app->path('foo', function($request) use($app) {
    return "foo";
$app->path('bar', function($request) use($app) {
    $foo = $app->run('GET', 'foo'); // $foo is now a `Bullet\Response` instance
    return $foo->content() . "bar";
echo $app->run('GET', 'bar'); // echos 'foobar' with a 200 OK status

Running Tests

To run the Bullet test suite, simply run vendor/bin/phpunit in the root of the directory where the bullet files are in. Please make sure to add tests and run the test suite before submitting pull requests for any contributions.


Bullet - and specifically path-based callbacks that fully embrace HTTP and encourage a more resource-oriented design - is something I have been thinking about for a long time, and was finally moved to create it after seeing @joshbuddy give a presentation on Renee (Ruby) at Confoo 2012 in Montréal.