I have a friend going to the Philippines on Monday and will book his ticket to Manila at the airport. He wants to get an extension visa for 59 days stay. Can he book a flight for 59 days and purchase the extension visa at Manila when he arrives or must he book a 30 day ticket, then buy a visa at Manila then change his ticket to 59 days which of course will be expensive. Any replies before Monday 27th March would be gratefully appreciated.
UK gov advice on your question https://www.gov.uk/foreign-travel-advice/philippines/entry-requirements
Personally, I have never been asked to show a return ticket on immigration to the Phils. On one occasion, I even flew there on a one way ticket. They usually ask you how long you plan to stay and that's it. To be cheap, he could book the flight for 59 days, arrive and say that you plan to stay for 3 weeks, and then apply for the extension of the visa. However, if your friend wishes to do everything by the book, then he will have to book a ticket that can be amended and do as you suggested, bearing the expense.
Book the ticket for the full period he intends to stay... IF he is a British citizen. The airlines are aware that we (Brits) are able to extend our initial 30 day waiver after arriving in the Phils. I did this for my last trip (Nov/Dec 2016).
It is not Philippines immigration that are demanding the onward ticket, note it does not have to be a return ticket, just a ticket out of Philippines. It is the airline carriers that need to see it, because if for any reason, you are refused entry, it is the airline that will will face a heavy fine. Hence it will be at at the check in where you board the flight to Philippines where you will be asked to show an onward ticket. I was caught out once without a ticket, Singapore in fact, and I had to purchase one before being allowed to check in. Always make sure I have a return or onward ticket since that.