I think we can all be a little definite about the spelling of our current surnames.
In the past though not all of our forebears could read and write and were reliant on those who could to record information for official documents. So when they transcribed an entry for a person, possibly having to interpret an accent as well it may not have come out exactly as we write it now.
Asa case in point one set of my ancestors has the name Ramage, the entries for them have been all spellings ranging from Rumage, Rimmadge rammage, Ramadge etc etc. I would be be a foolish researcher to disregard these spellings because some later educated ancestor has decided that Ramage is the spelling.
I suggest you keep the Philp and all variations including the Philip/Philips/Philps in your seaching tool kit.