All components of salary which are universally paid/ paid to all employees of your organisation without reference to skill, residence, cost of travel etc shall attract PF contributions. According to EPF Act Pf is to be contributed on basic salary and dearness allowance. Now basic salary means total salary. Only over time allowance, bonus, commission, house rent allowance or similar allowance shall be out of the scope of wages. Even house rent allowance paid universally/ all employees without reference to their residential status as to whether they reside in rented house or not, whether spouse is getting HRA or not, should fall within the scope of wages. Still, since the same is there in the exclusion part of the definition of basic wages, you can exclude HRA. But you should pay PF on other allowances fixed as part of contract of employment.
At the same time, if the gross salary (or gross salary less HRA) is more than Rs 15000, the employer is bound to pay PF on Rs 15000 only.