where and or where in laravel code example

Example 1: laravel where

$users = DB::table('users')
                ->whereMonth('created_at', '12')
                ->get();

Example 2: or where in orm laravel

$a='foo', $b='bar', $c='john', $d='doe';

Coder::where(function ($query) use ($a, $b) {
    $query->where('a', '=', $a)
          ->orWhere('b', '=', $b);
})->where(function ($query) use ($c, $d) {
    $query->where('c', '=', $c)
          ->orWhere('d', '=', $d);
})->get();