Set client routing for WordPress

functions.php

// Get current route
function vsi_get_current_route(){
    $routeWithParams = explode('/', $_SERVER['REQUEST_URI'])[1];
    return parse_url($routeWithParams, PHP_URL_PATH);
}

add_filter( '404_template_hierarchy', 'vsi_client_routing' );

function vsi_client_routing() {
	$router = new CompanyRouter();

	$currentRoute = vsi_get_current_route();
    
    // if there is a defined client side route /contacts
    // render / only for specific 404 routes, but not for all. Remove the check for all
    if($currentRoute === 'contacts'){ 
        status_header(200);
        // Set the title
        add_filter("pre_get_document_title", function($old_title){
            return "Contacts";
		});
		return locate_template( array('index.php'));
	}
}