How do I pass data in parent Iframe to Iframe?

I have this site "www.example.com/gamesite.php", and I also have a game developed using construct 3 uploaded at example.com/games/wargame

In gamesite.php, I serve "wargame" using an Iframe. Also, in gamesite.php.. I have a user authenticate and keep the data in $_SESSION.

What I want is, the game to recognize the user that currently play using $_SESSION.

How do I do that? or maybe there's another approach...

Thanks

Not sure if this will be helpful, but check out this link:

howtoconstructdemos.com/communicating-with-an-iframe-in-construct

Not sure if this will be helpful, but check out this link:

https://howtoconstructdemos.com/communicating-with-an-iframe-in-construct/

Thank you, any ideas I appreciate.