compare collections and get values from one that aren't in the other

example.php

<?php
// Given 2 collections of nested, indexed arrays, 
// find the items in the first array that are not 
// found in the second array using a given key

// in this example, find items in $collection1 that 
// are not found in $collection2, and return all of 
// them as a new collection
$collection1 = collect([
    ['product' => 'Desk', 'price' => 200],
    ['product' => 'Chair', 'price' => 100],
]);

$collection2 = collect([
    ['product' => 'Desk', 'price' => 200],
    ['product' => 'Lamp', 'price' => 130],
]);

$diff = $collection1->someMethod($collection2, 'product');

$diff->all(); 

// [
//     ['product' => 'Chair', 'price' => 100]
// ]


///////////////////////////////////////////////////
/// UPDATE
///////////////////////////////////////////////////
$diff = $collection1->filter(function($item) use ($collection2) {
        return ! $collection2->contains('product', $item1->get('product'));
    });

$diff = $collection1->flatten()->diff($collection2->flatten(), 'product');

thanks!