Layover 12 hours

If your itinerary is:

Dubai - Guangzhou - Manila

And your layover in Guangzhou is 12 hours, you are perfectly eligible for 24 hour visa free transit and you don't need any kind of visa.

Assuming that you will travel on China Southern single (through) ticket, you should definitely be eligible for a hotel accommodation provided by the airline and you should claim one. If you do that successfully, you will print out your accommodation confirmation along with your flight tickets and you will declare in Dubai that you will travel to Manila via Guangzhou using 24 hour visa free transit. After a short inspection, you will be allowed to board the plane.

Upon your landing in Guangzhou, you will immediately approach 24 hour visa free transit where you will apply for a temporary entry permit and here you will also present your accommodation confirmation. Since your layover is quite long one, your chances to be allowed to exit the airport are fine and I hope you will be allowed to spend your time by exploring the city and by resting in your accommodation. Anyway, you should be aware that the issuing of a temporary entry permit always depends on discretion of immigration authorities on a day of arrival.