The consideration is £47.1mln for the acquired centres with a further £6.9mln payable for the additional two.
PHP said that the acquired properties are leased to GPs, NHS operators or pharmacies with 91% of their rental income backed by the UK government.
The deal will increase the size of FTSE250- group's portfolio to 510 properties worth just under £2.5bn and with annual rents of £131mln.
Nearly all of the rents from its portfolio are guaranteed by either the UK or Irish governments and PHP said it had received 98% of rents due for its second quarter with only around £800,000 outstanding.
In a statement, Harry Hyman, PHP’s managing director, said: ”We believe that the portfolio presents several good opportunities to enlarge the premises, extend the lease terms and obtain an uplift in rent, as the majority of the medical centres represent key facilities within their local healthcare economy.
"The current coronavirus pandemic is expected to reinforce the need for modern, integrated primary care facilities to relieve pressure on hospitals and A&E facilities. The company's portfolio is extremely well placed to deal with the current COVID-19 pandemic and resulting economic disruption, as it supports the UK primary healthcare system.”
PHP has undrawn loan facilities and cash of £298mln following the latest purchase and a strong pipeline of opportunities in both the UK and Ireland for additional selective acquisitions and developments, he added.