code works from console, but doesn't work in method

I made sqlite database using doctrine 2. When i run create_product.php from console it works fine, but i want to create product from php class. So i made method with create_product.php code and included bootstrap.php, but i had issue: Undefined variable: entityManager.

create_product.php

<?php
// create_product.php
require_once "bootstrap.php";

    $name = 'name';
    $date = date("d.m.Y");
    $time = time();

    $product = new Product();
    $product->setName($name);
    $product->setSaveDate($date);
    $product->setSaveTime($time);

    $entityManager->persist($product);
    $entityManager->flush();
echo "Created product with ID " . $response->getId() . "\n";
?>

and php class file:

<?php
namespace app\monitor;
use Product;

require_once dirname(dirname(dirname(__DIR__))) . "/bootstrap.php";

class Service {

$this->saveProduct('name');   

public function saveProduct($name) {

        $date = date("d.m.Y");
        $time = time();

        $entity = new Product();
        $entity->setName($name);
        $entity->setSaveTime($time);
        $entity->setSaveDate($date);

        $entityManager->persist($entity);
        $entityManager->flush();
    }
}

Why it's work from console, but doesn't work in method?