I believe you've misinterpreted the use of the word "dummy" here: it's in the 
adjective meaning of "placeholder", not the vaguely insulting noun form.

Yes, I understand the usage of that particular word. That word, in and of itself 
is not the issue. The primary issue is that the phrase

"This is a dummy manual entry to satisfy those people who are looking for 
unlink() or unset() in the wrong place."

is unnecessarily condescending, as though your are speaking to an annoying 
sibling or co-worker. The secondary, and perhaps most important issue is that it 
is simply technically incorrect: one need not "look in the wrong place" for this 
term, one simply types the word 'delete' into the search field on the PHP 
documentation web page and this entry is presented TO them.

The word 'delete' is a perfectly reasonable word to search for in a programming 
language reference. If it is not a valid term for the reference being searched, 
then display a message notifying the searcher of that fact. Do not assume that 
you have determined the "true meaning" of their inquiry, produce a result, and 
then proceed to tell them that THEY have looked in the WRONG place!