Fairly often in Drupal I get handed arrays that have significant keys, but the values are either a label or false-y. I generally don't care about the items with empty values, or I specifically want to remove them. The solution is to use array_filter($arr) to remove any array items with false-y values. In fact, sometimes I don't even care about the labels at all, in which case I might do array_keys(array_filter($arr)). Examples below.

array_filter() can also take a callback as the second argument, which lets you filter out items on your own terms. See the array_filter() documentation.