Can i combine Slim Framework with plain PHP

Question

I just started with PHP not too long ago and have done some small projects with just plain PHP + Ajax + html. I’m more comfortable with procedural code than OOP. I can still use OOP library of Pakagist. But i want to go slow the first time using a framework.

I want to do a serious new project with Slim but in a procedural way. My ideas:

Only use routing to require a view My Url: example.com/?r={child router}&page={view}

Routing: Only used to require to a child router and forward $parameter. Template & View: will receive a json result from ajax callback, my app will heavy ajax.

$app->get('/}', function() {
    require "index.view";
});
$app->get('/{route}/{page}', function (Request $request, Response $response, array $args) {
    $route = $args['route'] ? $args['route'] : "";
    $page = $args['page'] ? $args['page'] : "";
// I have a folder View contains folder User
    if folder_exists("route/" . $route)
    {
        if file_exists("view/" . $route . "/" . $page . ".php")
        {
            require ("view/" . $route . "/" . $page . ".php");
        } else {
            require ("view/" . $route . "/def_page.php");
        }
    } else {
      header (Location: index.php);
    }
});


// example.com/?r=user&page=register
// will require view/user/register.php

// example.com/?r=admin&page=login
// will require view/admin/login.php

And all my logic will be handled through an ajax route like

$app->get('/ajax/{route}/{action}', function (Request $request, Response $response, array $args) {
    $route = $args['route'] ? $args['route'] : "";
    $action= $args['action'] ? $args['action'] : "";
// I have a folder View contains folder User
    
        if file_exists("ajax/" . $route . "/" . $page . ".php")
        {
            require ("ajax/" . $route . "/" . $page . ".php");
        } else {
            $result = [
                        'status' => false,
                        'msg' => 'failed'
            ]
            return json_encode($result);
        }
});

// example.com/?r=ajax&action=login
// will require ajax/user/login.php

Please help me and let me know if this doesn’t fit in Slim or anything bad. Thanks for help.

UPDATE: I used this route library. It very simple and nice. Slim 4, he's slim but very complex.

<?php
use Core\Libs\View;
use Core\Libs\Config;

$route = new AltoRouter();

$route->map( 'GET', '/', ['route' => 'core', 'page' => 'landing']);

$route->map( 'GET', '/user', ['route' => 'user', 'page' => 'home']);

$route->map( 'GET', '/user/login', ['route' => 'user', 'page' => 'login']);

$match = $route->match();

?>
    Target: <?php var_dump($match['target']); ?><br>
    Params: <?php var_dump($match['params']); ?><br>
    Name:   <?php var_dump($match['name']); ?><br>
<?

if( is_array($match) && isset( $match['target'] ) ) {
    //call_user_func_array( $match['target'], $match['params'] );
    var_dump($match);
} else {
    header( $_SERVER["SERVER_PROTOCOL"] . ' 404 Not Found');
    echo 'Không tìm thấy trang';
}