Planetary host star designation (sometimes shortened as PHS designation) is a star catalog used exclusively to designate stars with planets using constellation and caelregio genitives or abbreviations. This catalog is very similar to variable star designation except it uses 'P' instead of 'V.' The 'P' is followed by a number without a space in between, then it succeeds to constellation or caelregio genitive or abbreviation with one space between 'P' designation and genitive or abbreviation.
Since the Sun passes through thirteen constellations in five caelregios annually instead of one, then it is designated not in constellation or caelregio genitives, but uniquely as P1 SoS, where SoS is the SOlar System.
Every time when a new planet is discovered around a star that previously had no known planet, then that parent star will receive a planetary host star designation with the next number after the last number within the constellation and caelregio. But when the new planet is discovered around a same star that already known to host planet(s), then the designation stays the same.