Help in creating a simple video chat with Video SDK in PHP and JS

Description
I’m trying to implement a simple 1-on-1 video chat with video sdk. I started studying the purejs-demo app. I don’t understand why there is a lot of nodejs stuff. I supposed that the video web sdk was just a javascript client library that connects to the zoom servers and enabled me to create some kind of video chat, but it seems i’m wrong. I’m not understanding why if the widget is on the browser there is a lot of server side stuff i’m not able to figure out. I’m just trying to create a video chat with javascript and PHP, but i’m having a really hard time. If someone can help i’ll be grateful. Thanks.

Error
I’ve tried running the purejs-demo but the server does not start and tells me that it’s unable to find @webpack-cli/serve command. I’ve tried to install it and rerun the command, but nothing change.

Which Web Video SDK version?
1.1.3