<?php

/**
 * 購入された商品の一覧を取得する（本来はDBなどから取得する想定）
 *
 * @return array<int, array{name: string, price: int, quantity: int, userId: int}>
 */
function getBoughtItemsAll()
{
    return [
        ['userId' => 1, 'name' => 'Apple', 'price' => 240, 'quantity' => 3],
        ['userId' => 1, 'name' => 'Banana', 'price' => 210, 'quantity' => 6],
    ];
}

/**
 * 指定されたユーザーIDに紐づく購入商品の一覧を取得する
 *
 * @return array<int, array{name: string, price: int, quantity: int, userId: int}>
 */
function getBoughtItemsByUserId($userId)
{
    $allItems = getBoughtItemsAll();
    $userItems = [];

    foreach ($allItems as $item) {
        if ($item['userId'] === $userId) {
            $userItems[] = $item;
        }
    }

    return $userItems;
}

/**
 * 購入商品の合計金額と平均金額を計算する
 *
 * @param array<int, array{name: string, price: int, quantity: int, userId: int}> $boughtItems
 * @return array{total: int, average: float}
 */
function summary($boughtItems)
{
    $total = 0;
    foreach ($boughtItems as $item) {
        $total += $item['price'] * $item['quantity'];
    }

    $average = $total / count($boughtItems);

    return [
        'total' => $total,
        'average' => $average,
    ];
}

function main()
{
    $currentUserId = 2;
    $boughtItems = getBoughtItemsByUserId($currentUserId);

    $data = summary($boughtItems);

    var_export($data);
}

main();