public function load(ObjectManager $em)
{
$android = new Category();
$android->setName('Android');
$security = new Category();
$security->setName('Security');
$ios = new Category();
$ios->setName('IOS');
$wp = new Category();
$wp->setName('Windows-Phone');
$em->persist($android);
$em->persist($security);
$em->persist($ios);
$em->persist($wp);
$em->flush();
$this->addReference('category-android', $android);
$this->addReference('category-security', $security);
$this->addReference('category-ios', $ios);
$this->addReference('category-windowsPhone', $wp);
}