protected function mergeBindings(array ...$arrays): array {
		
		// at first blush, it seems like one could use something like array_merge()
		// to build our return value, but because that method would overwrite matching
		// keys in early arrays with values in the latter ones, we can't rely on it.
		// instead, what we actually want to do is flatten our $arrays which we've
		// learned to do here: http://stackoverflow.com/a/1320156/360838.
		
		$bindings = [];
		
		array_walk_recursive($arrays, function($x) use (&$bindings) {
			$bindings[] = $x;
		});
		
		return $bindings;
	}