Dog Vomiting White foam.?

My dogs was doing that several times a day. We took them to our vet who said it was a bacterial infection in their throat. She gave them antibiotics and they are all better. however please keep in mind your dog isn't a spring chicken anymore. He is old and need to take life slow. It could be old age getting to him. Just like humans when they get old. They have their good days and their bad days.