fire base sdk for php showing error for new Factory()

My code for tester.php

require __DIR__.'/../vendor/autoload.php';

use Kreait\Firebase\Factory;
$factory = (new Factory())->withServiceAccount('./../../landoflearners-firebase-adminsdk-v70d3-d7e08e3f89.json');
$auth = $factory->createAuth();

My directory structure

error

intelephense error

Undefined type 'Kreait\Firebase\Factory'

package.json

{
    "require": {
        "kreait/firebase-php": "^5.20"
    }
}