PHP使用foreach（）向元素添加元素

How to add elements to the array using the foreach loop?

    $list = [
        ['User-ID', 'Payout-ID', 'Amount', 'Withdraw address', 'Date'],
    ];

    //generate CSV
    foreach ($open_payouts as $open_payout) {
        $list .= [
            (string)$open_payout->user_id,
            (string)$open_payout->id,
            (string)number_format($open_payout->amount / 100000000, 8, '.', ''),
            (string)$open_payout->user->withdraw_address,
            (string)$open_payout->created_at,
        ];
    }

    $fp = fopen(app_path() . '/CSV/file.csv', 'w');
    //write whole list
    foreach ($list as $fields) {
        fputcsv($fp, $fields);
    }

It seems like my problem is located at $list .=. How to insert another array into this array, so I can generate a .CSV file from the arrays?

.= is used to concatenate strings - not arrays.

You simply need to use;

$list[] = [
        (string)$open_payout->user_id,
        (string)$open_payout->id,
        (string)number_format($open_payout->amount / 100000000, 8, '.', ''),
        (string)$open_payout->user->withdraw_address,
        (string)$open_payout->created_at,
    ];

That will add your new array onto the end of your $list array.

You could also use array_push();

array_push($list, [
    (string)$open_payout->user_id,
    (string)$open_payout->id,
    (string)number_format($open_payout->amount / 100000000, 8, '.', ''),
    (string)$open_payout->user->withdraw_address,
    (string)$open_payout->created_at,
]);