Salvar a imagem do perfil Facebook utilizando SDK V5

Ola, pesquisei bastante e não encontrei uma solução... Pois consigo acessar todos os dados que solicitei permissão, porém na hora de salvar a imagem em meu servidor tenho um arquivo salvo com 0KB e uma mensagem no arquivo log.

ERROR_LOG

[17-Aug-2016 00:07:50 America/New_York] PHP Warning: Illegal string offset 'url' in /home/*****/login.php on line 243
[17-Aug-2016 00:07:50 America/New_York] PHP Warning: file_get_contents(h): failed to open stream: No such file or directory in /home/*****/login.php on line 243
Segue o código

<?php
session_start();
require_once __DIR__ . '/src/Facebook/autoload.php';

$fb = new Facebook\Facebook([ 'app_id' => 'APP_ID', 'app_secret' => 'APP_SECRET', 'default_graph_version' => 'v2.4',

]);
$helper = $fb->getCanvasHelper();

$permissions = ['email']; // optionnal try {

	if (isset($_SESSION['facebook_access_token'])) {
	$accessToken = $_SESSION['facebook_access_token'];
	} else {
 $accessToken = $helper->getAccessToken();
	}

} catch(Facebook\Exceptions\FacebookResponseException $e) { // When Graph returns an error

 echo 'Graph returned an error: ' . $e->getMessage();
 exit;

} catch(Facebook\Exceptions\FacebookSDKException $e) { // When validation fails or other local issues

	echo 'Facebook SDK returned an error: ' . $e->getMessage();
 exit;
 }

if (isset($accessToken)) {

	if (isset($_SESSION['facebook_access_token'])) {
 $fb->setDefaultAccessToken($_SESSION['facebook_access_token']);
	} else {
 $_SESSION['facebook_access_token'] = (string) $accessToken;
 // OAuth 2.0 client handler
 $oAuth2Client = $fb->getOAuth2Client();
 // Exchanges a short-lived access token for a long-lived one
 $longLivedAccessToken = $oAuth2Client->getLongLivedAccessToken($_SESSION['facebook_access_token']);
 $_SESSION['facebook_access_token'] = (string) $longLivedAccessToken;
 $fb->setDefaultAccessToken($_SESSION['facebook_access_token']);
	}
	// validating the access token
	try {
 $request = $fb->get('/me');
	} catch(Facebook\Exceptions\FacebookResponseException $e) {
 // When Graph returns an error
 if ($e->getCode() == 190) {
 unset($_SESSION['facebook_access_token']);
 $helper = $fb->getRedirectLoginHelper();
 $loginUrl = $helper->getLoginUrl('https://apps.facebook.com/APP_NAMESPACE/', $permissions);
 echo "<script>window.top.location.href='".$loginUrl."'</script>";
 exit;
 }
	} catch(Facebook\Exceptions\FacebookSDKException $e) {
 // When validation fails or other local issues
 echo 'Facebook SDK returned an error: ' . $e->getMessage();
 exit;
	}
	// getting profile picture of the user
	try {
 $requestPicture = $fb->get('/me/picture?redirect=false&height=300'); //getting user picture
 $requestProfile = $fb->get('/me'); // getting basic info
 $picture = $requestPicture->getGraphUser();
 $profile = $requestProfile->getGraphUser();
	} catch(Facebook\Exceptions\FacebookResponseException $e) {
 // When Graph returns an error
 echo 'Graph returned an error: ' . $e->getMessage();
 exit;
	} catch(Facebook\Exceptions\FacebookSDKException $e) {
 // When validation fails or other local issues
 echo 'Facebook SDK returned an error: ' . $e->getMessage();
 exit;
	}

	// showing picture on the screen
	echo "<img src='".$picture['url']."'/>";
	// saving picture
	$img = __DIR__.'/'.$profile['id'].'.jpg';
	file_put_contents($img, file_get_contents($picture['url']));

 // Now you can redirect to another page and use the access token from $_SESSION['facebook_access_token']

} else {

	$helper = $fb->getRedirectLoginHelper();
	$loginUrl = $helper->getLoginUrl('https://apps.facebook.com/APP_NAMESPACE/');
	echo "<script>window.top.location.href='".$loginUrl."'</script>";
}

Consigo exibir a foto aqui:

echo "<img src='".$picture['url']."'/>";

Porém não consigo salvá-la utilizando...:

$img = __DIR__.'/'.$profile['id'].'.jpg';
file_put_contents($img, file_get_contents($picture['url']));

Alguém teria uma solução ou saberia o porque de não funcionar dessa forma?