laravel validation required if another field is present code example

Example 1: laravel required if another field has value

'last_name' => 'required_if:another_field,value'

Example 2: laravel form validation based on another field value

$validator = Validator::make($request->all(),[
        'program'           => 'required',
        'music_instrument'  => 'required_if:program.*,in:Music'
  ]);