Well you have an array of the first Phone?!
$phone = [
'reviews' => 'example'
];
$phone['reviews']; // example
Remove the first() if you don't want just the first, and the whole Collection to an array.
$phones = Phone::with('reviews','specifications','retailers')->get()->toArray();
As a Collection implements Arrayable/ArrayAccess you can loop as normal with the objects.
$phones = Phone::with('reviews','specifications','retailers')->get();
foreach($phones as $phone)
{
foreach($phone->reviews as $review)
{
$review; //
}
}
or if a phone has many reviews
$phone = Phone::with('reviews','specifications','retailers')->first();
foreach($phone->reviews as $review)
{
$review; //
}