Involved in degradation of methylphosphonate. Catalyzes the hydrolysis of the phosphate ester at carbon-1 of 5-phospho-D-ribose 1,2-cyclic phosphate to form ribose 2,5-bisphosphate. This intermediate is then hydrolyzed to ribose-5-phosphate and inorganic phosphate. alpha-D-ribose 1,2-cyclic phosphate 5-phosphate + H2O = D-ribose 2,5-bisphosphate + H(+) D-ribose 2,5-bisphosphate + H2O = D-ribose 5-phosphate + phosphate kcat is 2.0 sec(-1) for 5-phospho-alpha-D-ribose 1,2-cyclic phosphate. kcat is 7.4 sec(-1) for D-ribofuranose 2,5-bisphosphate. Belongs to the PHP family.