  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.
