Restler always returns 404: Not found

I have installed Restler on my local server to test and make some APIs for my project.

Api requests are handled via http://localhost/myproject/api/.

The problem is that everytime i try to make a request i get the following error:

{
    "error": {
        "code": 404,
        "message": "Not Found"
    },
    "debug": {
        "source": "Routes.php:383 at route stage",
        "stages": {
            "success": [
                "get"
            ],
            "failure": [
                "route",
                "negotiate",
                "message"
            ]
        }
    }
}

Also this is my .htaccess:

RewriteEngine on
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^api(.*)$ /myproject/api/api.php [QSA,L]

And this is what the api.php looks like:

namespace myproject;

use Luracast\Restler\Restler;

require_once($_SERVER["DOCUMENT_ROOT"]."/myproject/resources/engine/settings.php");
require_once(Settings\Path\Absolute::$library."/restler/vendor/restler.php");

$restler = new Restler();
$restler->addAPIClass("myproject\\User");
$restler->handle();

I guess there's some misconfiguration around, but i really can't figure out what's wrong.

(I also tried some solutions on Stackoverflow but they doesn't seem to work for me)

Edit:

I tried reaching the example using the following path http://localhost/myproject/resources/engine/library/restler/public/examples and they're working, so i guess it has to do with the configuration of Restler itself because it doesn't seem to work in http://localhost/myproject/api.

Furthermore i also tried copying the Restler Explorer in http://localhost/myproject/api/explorer and i keep receiving the error: 404 : Not Found ../resources.json probably because i didn't install Restler in the root folder of my project. How am I supposed to install Restler in a different subfolder?

Edit 2: I just moved the following class into the example 001 folder:

class User {

    function data() {

        return "HELLO!";
    }
}

and added this line inside the index.php of the example:

$r->addAPIClass('User');

If i try to run the example at .../_001_helloworld/index.php/say/hello it works without problems but if i try _001_helloworld/index.php/user/data it isn't.

At this point i have lost every hope and i really need help 'cause really i'm missing something but really can't guess what :( HELP!