$instagram = new instagram([  
  "key" => "API_KEY",  
  "secret" => "API_SECRET",  
  "callback" => "CALLBACK_URL"  
]);
echo '<a href="'.$instagram->loginUrl().'">Login with Instagram</a>';

$token  = $_GET["token"];
$instagram->setAccessToken($token);

$user_data  = $instagram->getUser();
echo '<pre>';
print_r($user_data);
echo '<pre>';