All components of salary that are universally paid, or paid to all employees of your organization without reference to skill, residence, cost of travel, etc., shall attract PF contributions. According to the EPF Act, PF is to be contributed on basic salary and dearness allowance. Now, basic salary means the total salary. Only overtime allowance, bonus, commission, house rent allowance, or similar allowances shall be out of the scope of wages. Even house rent allowance paid universally to all employees without reference to their residential status, such as whether they reside in a rented house or not, or whether their spouse is receiving HRA, should fall within the scope of wages. However, since it is included 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 the contract of employment.
At the same time, if the gross salary (or gross salary less HRA) is more than Rs 15,000, the employer is bound to pay PF on Rs 15,000 only.