what is the validity of visa particularly for F-Visa given for Philippine passport holder?

Generally, the validity of a single entry China visa is 3 months. But I have seen some got one with validity of only 7 days only. It depends on the visa officers actually.

Thanks Alvin. I'll be going to China next month for a business trip. However, I was informed that I will only be given a 30 days Visa validity which I think shouldn't be the case. I haven't got my Visa stamp yet. If I reapply for the visa stamping thru a diff officer. Is there a chance to get a 90 days validity?

If you were informed to be given a visa with 30 days validity. Then, take it, because you may get a same visa even you reapply from other office. It is a waste of money. The visa policy is getting tough due to the trouble between China and Philippines.