I seriously doubt you can make PHP convert anything to that exotic charset automatically even with creative configuration, and pretty much sure it wouldn't do a

I seriously doubt you can make PHP convert anything to that exotic charset automatically even with creative configuration, and pretty much sure it wouldn't do any of the sort in common configuration. What I suspect is going on is that the author is interested in exploiting PHP engine and is assuming PHP code using iconv() and wants to talk about how to get from there to full scale RCE. It is indeed a fascinating and non-trivial topic, though the relationship between a particular CVE and the PHP angle is rather coincidental - any buffer overflow would do, it's just the author happened to have one in a reasonably common function.