<?php
$warehouse = [
['name' => 'картошка', 'weight' => 100, 'price' => 100500],
['name' => 'морковка', 'weight' => 50, 'price' => 5000],
['name' => 'лук'     , 'weight' => 16, 'price' => 215],
['name' => 'оп'      , 'weight' => 1, 'price' => 999999]
];


$checkWeightIsLessThan100 = function ($item) {
return $item['weight'] < 100;
};

function findItems($warehouse, $checkWeightLessThan100){
	foreach ($warehouse as $item){
		if($checkWeightLessThan100){ //если вес меньше 100 то 
			return $item; //как можно вернуть сразу несколько значений в виде массива?
		} 
	}
};

$warehouse = FindItems($warehouse, $checkWeightLessThan100 );
var_dump ($warehouse);