Question UnityWebRequest text in WEBGL

I have a problem, I have this code:
In short, I make a post call to a site, which gives me an answer.
In editor it works, in build windows it works, but in build webgl it doesn't work, in the sense that the text does not give me anything (empty strnga).
Because? And how can I fix it?

Thanks for answer!

(below I also attach the php code)

 

First thing to check is CORS. Google that up, see what's involved, understand the process. Browsers run on a different security model than most other platforms.