Wallet API error

[pws2016]

Hello,
i try using the API Wallet and i creqte the API key in console with domain restriction.
But the code return me an error:
[{"message":"Login Required.","domain":"global","reason":"required","location":"Authorization","locationType":"header"}]

I use the PHP library and i write this code:
$client = new Google\Client(); $client->setApplicationName('Wallet Objects App'); $client->setDeveloperKey(GOOGLE_WALLET_API_KEY);

How i can fix this?

Thanks