Usually garlic doesn't fall over, unless you have gone way past harvest time. This year is an exception for me. The Turban type garlics (Tzan, Shantung purple, Thai Purple, etc) got stressed out by the weather this year. Probably the 1 degree temps in early April were too much for them since they are the earliest garlic and were pretty tall by then. When garlic is stressed by the cold, it can form strange looking bulbs or no bulbs at all, just "rounds".
The Turban garlics have very weak stems this year and most are laying flat on the ground. The very bottom leaves have yellowed or fallen off (as is normal a week before harvest time), but they are still 80% green.
I am digging the tiny bulbs up early (the ones with the skinniest stems) because I may not be able to find them later when they become more dried up. I am also digging any that half the leaves are yellow. The rest I'm leaving to see if they will bulb up in the next few days.
The "rounds" that I get (no cloves, just one round onion shaped bulb) will be saved for re-planting in the Fall. They will produce huge garlic bulbs for next year.