How to get Header in php using Slim Framework

tokenAuth.php

<?php
use \Psr\Http\Message\ServerRequestInterface as Request;
use \Psr\Http\Message\ResponseInterface as Response;

require 'vendor/autoload.php';
$app = new \Slim\App;

$app->get('/',function($request,$response,$array)
{
    // $headers = apache_request_headers();

    // if (isset($headers['Authorization'])) 
    // {
    //     $api_key = $headers['Authorization'];
    //    echo $api_key;
    // } else {
    //     $data["error"] = true;
    //     $data["message"] = "Api key is misssing";
    //     return $response->withJson($data);
    // }

    // print_r($request->getserverParams());
    // print_r($request->getHeader());

    $tokon=$request->getserverParams()["HTTP_KANTAPP_COM"];

    if($tokon=='kantapp123456')
    {
        echo "Welcome to this site";
    }
    else {
        $data["status"]="Error";
        $data["message"]="Token is invalid";
        return $response->withJson($data,401);
    }
    
});


$app->run();