In the title compound, C(20)H(19)O(4)P, the dihedral angle between the phenyl rings is 73.3 (4)° and the dihedral angles between the benzene ring and the two phenyl rings are 43.0 (3) and 54.3 (1)°. In the crystal, O-H⋯O hydrogen bonds and weak O-H⋯O inter-actions are observed, which form a supra-molecular sheet parallel to (010).