Hi Christina,
You are right, you don’t need to add any international dialing codes when calling a Philippines cell located abroad. You don’t have to activate roaming to be able to call it. Most likely there is an issue with your friend’s phone. Maybe he doesn’t have roaming activated, or the phone is turned off. Hard to say. What you could do – call his wireless provider – they might be able to give you some details on his whereabouts (they could possibly tell you if his contract is still valid, or if he has been using his phone abroad, etc).
One thing I would like to clarify: I noticed you added digit 5 to your friend’s cell when trying to call him using Saudi Arabia and UAE’s country codes. Of course this couldn’t have worked. Apart from that, our pages provide information on how cell numbers look like in most countries. For these 2 countries for example, all cell numbers start with 5. If you have a cell number from these countries, it should already include the starting 5 (no need to add it again).
I hope this helps.