eloquent laravel group by year

controller.php

// Carbon
use Carbon\Carbon;   
$visitorTraffic = PageView::select('id', 'title', 'created_at')
    ->get()
    ->groupBy(function($date) {
        return Carbon::parse($date->created_at)->format('Y'); // grouping by years
        //return Carbon::parse($date->created_at)->format('m'); // grouping by months
    });

how to group by year and her months

// Carbon
use Carbon\Carbon;
$visitorTraffic = PageView::select('id', 'title', 'created_at')
->get()
->groupBy(function($date) {
return Carbon::parse($date->created_at)->format('Y-m'); // grouping by years and its month
});

Thank you @theinizio
bu i mean years and his months as child array

// Carbon
use Carbon\Carbon;
$visitorTraffic = PageView::select('id', 'title', 'created_at')
->get()
->groupBy(function($date) {
return Carbon::parse($date->created_at)->format('Y'); // grouping by years
})->map(function($traffic){
return $traffic->groupBy(function($date){
return Carbon::parse($date->created_at)->format('m'); // grouping by years
});
});

@theinizio thank you