I have been searching feverishly to try finding information on these bugs. When I saw the picture of one that another victim had submitted I immediately knew that was it. It actually started about 4 yrs ago with the tiny black bugs in my window sill that eventually got big enough to look like a regular fly. Then after a reputable pesticide company sprayed they almost all went away. Now however they are gathering 20-30 on my front steel door but that is where they also die. Any suggestions?
Management starts with an accurate identification of the pest. Phorid flies are quite small. When an adult fly ecloses (emerges as an adult from the pupal stage), they emerge at the size they will be for the rest of their lives; they will not "[get] big enough to look like a regular fly". Since you may be dealing with multiple specimens, we need to start with identification so that you can establish and implement a management plan.
Small specimens are difficult to photograph and identify accurately via electronic means. My suggestion is that you collect 5-10 of the flies in a clean plastic vial (pill bottle) filled with alcohol to preserve the specimens. Take the preserved specimens to your local University of Missouri Extension office (https://extension2.missouri.edu/locations) for accurate identification by an Extension Agent, an entomologist, or the University of Missouri Extension's diagnostic lab (usually diagnostic labs collect a fee for diagnostic services).
Once you get an accurate pest identification, the service (agent, entomologist, or lab) will likely offer management options and suggestions.