Differential cross sections at t=tmin and decay asymmetries for the γp→φp reaction have been measured using linearly polarized photons in the range 1.5 to 2.9 GeV. These cross sections were used to determine the Pomeron strength factor. The cross sections and decay asymmetries are consistently described by the t-channel Pomeron and pseudoscalar exchange model in the Eγ region above 2.37 GeV. In the lower energy region, an excess over the model prediction is observed in the energy dependence of the differential cross sections at t=tmin. This observation suggests that additional processes or interference effects between Pomeron exchange and other processes appear near the threshold region.