  A plateau phase in the X-ray afterglow is observed in a significant fraction
of gamma-ray bursts (GRBs). Previously, it has been found that there exists a
correlation among three key parameters concerning the plateau phase, i.e., the
end time of the plateau phase in the GRB rest frame ($T_{a}$), the
corresponding X-ray luminosity at the end time ($L_{X}$) and the isotropic
energy of the prompt GRB ($E_{\gamma,\rm{iso}}$). In this study, we
systematically search through all the \emph{Swift} GRBs with a plateau phase
that occurred between 2005 May and 2018 August. We collect 174 GRBs, with
redshifts available for all of them. For the whole sample, the correlation
between $L_{X}$, $T_{a}$ and $E_{\gamma,\rm{iso}}$ is confirmed, with the best
fit relation being $L_{X}\propto T_{a}^{-1.01}E_{\gamma,\rm{iso}}^{0.84}$. Such
an updated three-parameter correlation still supports that the central leftover
after GRBs is probably a millisecond magnetar. It is interesting to note that
short GRBs with duration less than 2 s in our sample also follow the same
correlation, which hints that the merger production of two neutron stars could
be a high mass magnetar, but not necessarily a black hole. Moreover, GRBs
having an "internal" plateau (i.e., with a following decay index being
generally smaller than -3) also obey this correlation. It further strengthens
the idea that the internal plateau is due to the delayed collapse of a high
mass neutron star into a black hole. The updated three-parameter correlation
indicates that GRBs with a plateau phase may act as a standard candle for
cosmology study.
