由于list()试图分配两个变量，因此它试图访问两个数组元素[0]和[1].因为该行上没有逗号，所以[1]不存在.

Since list() is attempting to assign two variables it is attempting to access two array elements [0] and [1]. Because there is no comma on the line, [1] does not exist.

尝试一些不同的功能:

$csv_data = file("data3_received.csv", FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);

foreach($csv_data as $line) {
    $data[] = str_getcsv($line);
}

要获取单个变量，您需要检查是否有多于一列或类似内容:

To get individual variables you need to check if you have more than one column, or something similar:

if(count($data = str_getcsv($line)) > 1) {
    list($service_id, $ki3) = $data;
} else {
    $service_id = $data[0];
}