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First, don't embed your PHP code like that. Separate your HTML from the PHP code. Second, don't use * in your select. Extract only those variables you plan to actually use. To do what you want, you need to create a form that submits your data when you click one of the buttons. See this article about using forms and passing data to PHP.

I agree with Requinix. The better approach (if you really need to do this) is what cruise ships have been doing for years. When passengers come back on board they line up and go thru a metal detector (of course!) and a baggage check and they scan their id card that was created when they arrived for their trip. This card is linked to a photo taken by the registration staff and when the card is scanned a picture shows up so that the crew knows for sure that the person now boarding is the person who is registered to that card - just like what you want to know. The difference is they rely on a staff member doing the immediate supervision of this interaction, not a computer check in a back office. (I hope I made sense here)

If someone doesn't want to be seen they'll just hide from the camera. Or worse, they'll take their own picture of the person they want to log in as and use that. Know that this is not real security. But as said, yes: you can use Javascript to get a still from the camera, then upload that like any other file.