Please tell me why an empty array is written to the variables

$January = $articles->whereMonth('updated_at','01')
  ->whereYear('updated_at', $year)
  ->get();

$February = $articles->whereMonth('updated_at','02')
  ->whereYear('updated_at', $year)
  ->get();

If there is no data in $January, then an empty array is written to $February regardless of the data availability. Tell me how to fix it and why is this happening?