@Hi Harry,
I haven't read your timeline if you have received a PPR already. But in my case I received PPR last March 4, send the passports including pictures & appendix A ( March 15), e-cas status change into "Decision made- medicals had been received" (April 6) and received the passports with visa (April 9- they delivered even it's holiday). I strongly suggest that you should not purchase tickets unless you receive your passports w/ visa. Anyway, the Visa officer will give you enough time to prepare for your departure. Like in my case our visa will expire until December(Note that the expiration of the visa is 1 year from the date of your Medical exam was done).
Btw, do you have accompnying children? If so, you still need your passports w/ visa in the DOT (Department of Tourism) for the reduce travel tax & Tax Exempt for your children ( Sayang din kasi discount for the tickets- less P1,620 each for infants & P810 for children ages 2-12y/o) when you purchase your tickets.
But if you receive your passports w/ visa already yes you can purchase your tickets by July, atleast 1 month before your intended date of departure, peak season daw kasi yun june & july that's why you need to make reservation to the travel agency.
Thanks & goodluck..
candy