<?php
$warehouse = [
['name' => 'картошка', 'weight' => 100, 'price' => 100500],
['name' => 'морковка', 'weight' => 50, 'price' => 5000],
['name' => 'лук'     , 'weight' => 16, 'price' => 215],
['name' => 'оп'      , 'weight' => 75, 'price' => 'Бесценен']
];

function findByName($warehouse, $name){
	foreach($warehouse as $wares){
		 if ($wares['name'] == $name){
		 	return $wares;
		 };

	}
}

$name = 'лук';
$name = findByName($warehouse, $name);
print_r ($name);