How to make PHP and React JS friends?

Question

PHP

I just started learning Node + React JS, Redux. Full kettle.
Dear gurus, poke your finger in solving this problem.
There is a small real estate site on smarty php. All requests are made through the MYSQL database.
Tell me (if there is such a solution, but it’s better to show an example or links to specific documentation with examples) how to make it right that in Reacte it was possible to receive and send requests from mysql?
example:
connected react

<script src="https://unpkg.com/[email protected]/umd/react.development.js" crossorigin></script>
<script src="https://unpkg.com/[email protected]/umd/react-dom.development.js" crossorigin></script>
<script src="https://unpkg.com/[email protected]/babel.js"></script>
<!-- мой файл react js -->
<script type="text/babel" src="{$estate_folder}/template/frontend/{$current_theme_name}/js/main.js"></script>

then I make a selection from the database on smarty php

private function getAgents()
    {
        $ret = array();
        $DBC = DBC::getInstance();
        $query = 'SELECT * FROM ' . DB_PREFIX . '_user WHERE group_id<>4 AND login<>\'_unregistered\' ORDER BY RAND() LIMIT 3';
        $stmt = $DBC->query($query);

        if ($stmt) {
            while ($ar = $DBC->fetch($stmt)) {
                $ret[] = $ar;
            }
        }
        $js_obj = json_encode($res);
        $this->template->assign('agentslist_items', $ret);
    }

then I display it in smart via foreach, I will not write the full output, let's just say that everything is given to the template using the means.
but if you include the $js_obj variable itself, then it is empty

{literal}
<script>
    var obj=$js_obj; 
    alert(obj);
</script>
{/literal}

Answer 1

Don't combine React and PHP in the same application. Create two different projects.
And reduce all communication between them to REST, for example.
Use your build systems in these different projects (some kind of crutch for both will not lead to anything good, they tried in Laravel). Place them on different subdomains then in production.

Answer 2

They don't do that. The meaning of the react is lost.
The whole point of js frameworks is to separate the frontend into a separate application that works with the backend via api. And what will be there on the back - laravel, pure php, node or python - it does not matter at all.
React is a state-oriented product. We work from the state. Php is a pure mvc classic.