how to get the username of the os that uploaded my website using PHP?

i'm creating a website that send Rest API to Jenkins to execute jobs with limited parameters.

the site is ready, and the last thing i need to add to it, is the username of the os that loaded my website.

if my user name is "Wizzz" and i loaded the webpage http://10.20.30.40:8080 then the page will tell me: "Hello Wizzz"

and if my username is "Ozzz" the webpage will tell me: "Hello Ozzz"

i try using get_current_user() but it returned me the web server username, and evn('username') returned nothing.

any idea?