The contributions of direct knockout processes, in addition to the diffractive production and one-pion-exchange processes associated with the phi-rho-pi and phi-gamma-pi couplings, to the polarization observables of the phi photoproduction from proton are calculated. We make use of Pomeron-photon analogy and a relativistic harmonic oscillator quark model. We find that some of the double polarization observables are very sensitive to a possible (s s-bar) admixture in the proton. It arises from the difference in the spin structures of the three different amplitudes. This suggests that such measurements could be very useful to probe the strangeness content in the proton.