VK API how to get userID in iframe application?

Question

PHP

VK API how to get userID in iframe application, preferably in PHP

Answer 1

From $_REQUEST['viewer_id'].
Other variables passed by Iframe to the application can be found here: vk.com/dev/apps_init .

Answer 2

echo $_GET['viewer_id'];
Don't thank.

Answer 3

You google, not set tasks for us here.
And so - here:
Then display the avatar