Once the food gets into the esophagus, this organ propels it down into the stomach by a series of rhythmic muscular contractions similar to what you see a snake use in moving forward. Although moving the food from the stomach into intestines is not, strictly speaking, part of swallowing, if the stomach fills or there are problems in the intestines, protective reflexes can prevent swallowing. This form of dysphagia is known as oropharyngeal dysphagia. It sounds like your father may have oropharyngeal dysphagia. The symptoms of this form of the disorder include coughing, choking and regurgitation immediately after attempting swallowing.
Liquids are more difficult to swallow than solids.
As you've experienced, painful swallowing and difficulty in speaking may also be present. A variety of mechanical and neuromuscular conditions can disrupt the oropharyngeal phase of swallowing and cause dysphagia. They include physical and congenital abnormalities, trauma, infections, tumors, inflammation of the esophageal lining and muscle disorders. Your father's condition may also be caused by an inflammation resulting in the swelling of the epiglottis, called epiglottitis. This inflammation is caused by a viral or bacterial infection and is treated by antibiotics.