There's no real answer since the term "propagate" can mean one of several things. For example are we propagating the session ID from the server to client or client to server? And in both cases there are several answers which apply.
PHP Dev or not, that question is too vague to be answerable. You'd have to ask additional questions just to understand the question itself.
As you would expect, Upwork doesn't have the resources for people that really know PHP to be doing these verifications. While we all agree that the question was poorly-worded, anyone with decent communication skills (a much-needed skill for people doing the kinds of client-facing software engineering jobs that are on Upwork) can easily recognize this and work with the non-technical person conducting the interview to arrive at the "right" answer even though it "DOES NOT COMPUTE" to the overly-pedantic "language lawyer" in some.
I remember someone angrily posting on HN about failing an HR phone screening because they tried arguing with the interviewer that Linux was not Unix, but was Unix-like (a sign that the interviewee clearly knew the one-word _expected_ answer that was on the interviewer's answer key). Just answer the very simple question and move on, instead of trying to show off or whatever. Part of functioning in the workplace means communicating effectively and professionally (by not being condescending, for example) with other people that may have different skill sets. The best engineers are very cognizant of this.
PHP Dev or not, that question is too vague to be answerable. You'd have to ask additional questions just to understand the question itself.