If a man walks in front of the worshipper it does not interrupt his prayer, but it detracts from its reward. Animals passing in front of the praying person do not interrupt the prayer. The Sunnah indicates that the one who is praying should prevent anything or  anyone who wants to pass in front of him even if they are not one of those three, neither a dog nor a woman nor a donkey. It is Sunnah for the believer to put something in front of him before he prays, such as a chair or a spear that he sticks in the ground, or a wall or pillar that he faces towards when he is praying so that nothing will pass in front of him that could interrupt his prayer.

As phlegm is pure and is not food or drink, and does not come under the same rulings as food and drink, if a person swallows while praying, the prayer remains valid, especially if one could not help it and was not able to spit it out into a handkerchief and the like.