Oh okay. So as @BarryCarlyon said you should do that with cURL([see here for the official curl PHP manual])(https://www.php.net/manual/en/book.curl.php). Although something like that is already implemented in Twitch. It would require one of your friends to be a Twitch Partner, which is probably not the situation here. But if one of your friends is a partner, he can just create a Twitch team and invite the other ones in there. Then you have an overview page about the team, where everyone is listed(who is currently streaming) and is sorted by viewer count. Read here for more: https://help.twitch.tv/s/article/twitch-teams?language=en_US
But I guess, you want to go with the programming it yourself approach. So take a look at the manual page of cURL and just put a reply here if you got any questions or encounter any issues ^^