i am fetching from Facebook API for Facebook Page but it returned me as Black diamond with question
$pictureObj = file_get_contents("https://graph.facebook.com/$page_id/picture?type=large");
You need to use an Access Token:
$pictureObj = file_get_contents('https://graph.facebook.com/' . $page_id . '/picture?type=large&access_token=xxxx');
More information about Tokens and how to generate them: