private function isInRect(ob:FlxObject,rect:Rectangle):Boolean {
			if ((ob.right) >= rect.x 
				&& (ob.left) <= (rect.x + rect.width)
				&& ob.bottom >= rect.y
				&& ob.bottom <= rect.y + rect.height // change bottom to top if you allow objects feet should go beyond rectangles bottom.
			) {
				return true;
			}else {
				return false;
			}
		}

private function isInRect(ob:FlxObject,rect:Rectangle):Boolean {
			if ((ob.right) >= rect.x 
				&& (ob.left) <= (rect.x + rect.width)
				&& ob.bottom >= rect.y
				&& ob.bottom <= rect.y + rect.height 
			) {
				return true;
			}else {
				return false;
			}
		}

Simple snippet to check is Flixel's flxObjects position according to a rectangle.
It will return true if it's inside the rectangle, false if not.

Very basic primitive box collision checking.

Check if the FlxObject is inside the given rectangle

flash

ActionScript 3