$products = [
10 => ['product_id' => 10, 'name' => 'Товар 1'],
15 => ['product_id' => 15, 'name' => 'Товар 2'],
25 => ['product_id' => 25, 'name' => 'Товар 3'],
26 => ['product_id' => 26, 'name' => 'Товар 4']
];
unset($products[15]);
print_r($products);