how to correctly return public server address in EC2 instance with PHP

Я новичок в AWS ... Я установил один экземпляр EC2, на котором работают Nginx и PHP 7.1.6. i have also made a page that return phpinfo(); details but it returning not my elastic IP but internal IP address:

$_SERVER['SERVER_ADDR'] 172.31.9.228

My EC2 has correctly associated one elastic IP and also trying browsing website everything running smooth.

There is a way to let Nginx returns public IP instead of private one?