.
+-- classes
|   +-- Database.php
|   +-- Route.php
+-- controllers
|   +-- AboutUs.php
|   +-- Controller.php
+-- views
|   +-- about-us.php
+-- .htaccess
+-- index.php
+-- routes.php

<?php

class Database{

    public static $host = 'localhost';
    public static $dbName = 'cms';
    public static $username = 'root';
    public static $password = '';

    private static function connect(){
        $pdo = new PDO('mysql:host='.self::$host.';dbname='.self::$dbName.';charset=utf8', self::$username, self::$password);
        $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        return $pdo;
    }

    public static function query($query, $params = array()){
        $statement = self::connect()->prepare($query);
        $statement->execute($params);
        if(explode(' ', $query)[0] == 'SELECT'){
            $data = $statement->fetchAll();
            return $data;
        }
    }
}

?>

<?php

class Route {
    public static function get($route, $function){
        //get method, don't continue if method is not the
        $method = $_SERVER['REQUEST_METHOD'];
        if($method !== 'GET'){ return; }

        //check the structure of the url
        $struct = self::checkStructure($route, $_SERVER['REQUEST_URI']);

        //if the requested url matches the one from the route
        //get the url params and run the callback passing the params
        if($struct){
            $params = self::getParams($route, $_SERVER['REQUEST_URI']);
            $function->__invoke($params);

            //prevent checking all other routes
            die();
        }
    }

    public static function urlToArray($url1, $url2){
        //convert route and requested url to an array
        //remove empty values caused by slashes
        //and refresh the indexes of the array
        $a = array_values(array_filter(explode('/', $url1), function($val){ return $val !== ''; }));
        $b = array_values(array_filter(explode('/', $url2), function($val){ return $val !== ''; }));

        //debug mode for development
        if(true) array_shift($b);
        return array($a, $b);
    }

    public static function checkStructure($url1, $url2){
        list($a, $b) = self::urlToArray($url1, $url2);

        //if the sizes of the arrays don't match, their structures don't match either
        if(sizeof($a) !== sizeof($b)){
            return false;
        }

        //for each value from the route
        foreach ($a as $key => $value){

            //if the static values from the url don't match
            // or the dynamic values start with a '?' character
            //their structures don't match
            if($value[0] !== ':' && $value !== $b[$key] || $value[0] === ':' && $b[$key][0] === '?'){
                return false;
            }
        }

        //else, their structures match
        return true;
    }

    public static function getParams($url1, $url2){
        list($a, $b) = self::urlToArray($url1, $url2);

        $params = array('params' => array(), 'query' => array());

        //foreach value from the route
        foreach($a as $key => $value){
            //if it's a dynamic value
            if($value[0] == ':'){
                //get the value from the requested url and throw away the query string (if any)
                $param = explode('?', $b[$key])[0];
                $params['params'][substr($value, 1)] = $param;
            }
        }

        //get the last item from the request url and parse the query string from it (if any)
        $queryString = explode('?', end($b))[1];
        parse_str($queryString, $params['query']);

        return $params;
    }
}

?>

<?php

class AboutUs extends Controller{

}

?>

<?php

class Controller extends Database{

    public static function CreateView($viewName, $urlParams = null){
        require_once('./views/'.$viewName.'.php');
    }
}

?>

<h1>About Us</h1>

RewriteEngine On

RewriteRule ^([^/]+)/? index.php?url=$1 [L,QSA]

<?php

    function loadClasses($class_name){
        $classesPath = './classes/'.$class_name.'.php';
        $controllersPath = './controllers/'.$class_name.'.php';

        if(file_exists($classesPath)){
            require_once($classesPath);
        }else if(file_exists($controllersPath)){
            require_once($controllersPath);
        }
    }

    spl_autoload_register(loadClasses);

    require_once('routes.php');
?>

<?php

Route::get('/about-us', function(){
    AboutUs::CreateView('about-us');
});

?>

//check the structure of the url
$struct = self::checkStructure($route, $_SERVER['REQUEST_URI']);

//if the requested url matches the one from the route
//get the url params and run the callback passing the params
if($struct){
    $params = self::getParams($route, $_SERVER['REQUEST_URI']);
    $function->__invoke($params);

    //prevent checking all other routes
    die();
}

/users/:username
/users/:username/photos
/users/:username/photos/:photoId
/users/:username/photos/:photoId?showComments=false

/users/jake1990
/users/jake1990/photos
/users/jake1990/photos/931280134
/users/jake1990/photos/931280134?showComments=false

Array -> [params => [username => jake1990], query: []];
Array -> [params => [username => jake1990], query: []];
Array -> [params => [username => jake1990, photoId => 931280134], query: []];
Array -> [params => [username => jake1990, photoId => 931280134], query: [showComments => false]];