REST Controller for PHP Applications

I keep coming up with ideas for projects that would benefit from a REST architecture. I am now laying out some foundations to build those projects on top. One of the projects involves very little code and I do not want to use a full fledged framework there. Another one is using Code Igniter which does not handle REST by default (as far as I can tell). So I wrote a minimal REST application controller that easy to integrate and very flexible.

It provides a base class that you would extend your actual controller from and you implement only the request types your are going to need.

<?php
class My_Controller extends REST_Controller
{
    function _get()
    {
        // handle get request
    }

    function _post()
    {
        // handle post request
    }

    function _delete()
    {
        // handle delete request
    }

    // do not care for put
}
?>

Quite easy so far. The REST_Controller defines two convenience methods.

_respond($body, $headers = array()) lets you send a HTTP response custom headers.

_respondError($error) allows you to send a HTTP status message back to the client. It will detect the request’s HTTP version and will create an appropriate reply.

The only thing you need to do is call the _dispatch() method when you want to start processing a request. I do happen to have an index() method for that:

<?php
class My_Controller extends REST_Controller
{
    function index()
    {
        $this->_dispatch();
    }

    function _get()
    {
        // handle get request

    }

    ...
}
?>

The REST_Controller is just a very bare-bones class that doesn’t handle input filtering or making request data available. That is all up to you.

In Code Igniter My_Controller looks like this:

<?php
// my parent class definition class lives next door
include dirname(__FILE__)."/rest_controller.php"; 

class MY_Controller extends REST_Controller
{
    function My_Controller()
    {
        // as per Code Igniter setup guide
        parent::REST_Controller();
    }

    function index($id)
    {
        // let's have others do the work
        $this->_dispatch($id);
    }

    function _get($id)
    {
        $this->load->model("json");
        $resource = $this->json->fetch_resource($id);
        $this->_respond($resource, $headers = array("Content-Type" => "application/json"));
    }

    function _delete($id)
    {
        $this->load->model("json");
        $resource = $this->json->fetch_resource($id);
        if(!$id || !$resource) {
            $this->_respondError("404 Not Found");
        }

        $this->json->delete($id);
    }

    ...
}
?>

Finally, here is the code. This is public domain free. Please report bugs or enhancements. Contact information can be found on my about page.

<?php
/*
Public domain PHP REST Controller Base Class.
Originally by Jan Lehnardt <jan@php.net>
Usage instructions: http://jan.prima.de/~jan/plok/archives/115-REST-Controller-for-PHP-Applications.html
*/
class REST_Controller extends Controller
{
    var $method = 'get'; //default
    function REST_Controller()
    {
        parent::Controller();
    }

    function _dispatch($id = false)
    {
        if(isset($_SERVER['REQUEST_METHOD'])) {
            $this->method = strToLower($_SERVER["REQUEST_METHOD"]);
        }
        $dispatch_method = "_{$this->method}";
        if(!is_callable(array($this, $dispatch_method))) {
            $this->_respondError("501 Not Implemented");
            return false;
        }

        $this->{$dispatch_method}($id);
    }

    function _getProtocol()
    {
        $protocol = "HTTP/1.1";
        if(isset($_SERVER['SERVER_PROTOCOL'])) {
            $protocol = $_SERVER['SERVER_PROTOCOL'];
        }
        return $protocol;
    }

    function _respondError($error)
    {
        $protocol = $this->_getProtocol();
        header("$protocol $error");

    }

    function _respond($body, $headers = array())
    {
        foreach($headers AS $header => $value) {
            header("{$header}: {$value}");
        }
        echo $body;
    }
}