Why it is written Undefined variable $HTTP_SERVER_VARS, when I've prеssed RUN in vieworders2. php file?

Question

$DOCUMENT_ROOT =$HTTP_SERVER_VARS[
'DOCUMENT_ROOT' ] ;

......….....…..................
https://code.sololearn.com/w6HVcKlo8n8H/?ref=app

Answer 1

://That's not a valid file to open, there is nothing like txt file on sololearn