使用PHP对列进行CSV数据排序

Question

I've looked on Stack Overflow with no solution that seems to work. Know that I'm a newbie!

Suppose I have a file (data.csv) with the following contents:

year,total
1990,57.58
2011,73.28
1880,54.67
1996,53.41
1950,53.22
1979,52.76
1876,52.62
1883,52.35
1882,52.12
2018,52.23

...then import the data with PHP:

$csv = array_map('str_getcsv', file('data.csv'));

How would I sort both the year and total by the total column in ascending order (such that 1882/52.12 are under $csv[0] in the array and 2011/73.28 are under $csv[10]?

The following and a print($csv); does not seem to be getting the items in the right order:

function compare($a, $b) {
    return ($b[0][1] - $a[0][1]);
}
usort($csv, "compare");

Do I need to use typecasting? Thank you!

Answer 1

This will do the trick:

You have to modify the function like this:

function compare($a, $b)
{
    // here, comparing "total" column of each row:
    return $a[1] >= $b[1] ? 1 : -1;
}

And the new ordering will be:

            Array
            (
                [0] => Array
                    (
                        [0] => 1882
                        [1] => 52.12
                    )

                [1] => Array
                    (
                        [0] => 2018
                        [1] => 52.23
                    )

                [2] => Array
                    (
                        [0] => 1883
                        [1] => 52.35
                    )

                [3] => Array
                    (
                        [0] => 1876
                        [1] => 52.62
                    )

                [4] => Array
                    (
                        [0] => 1979
                        [1] => 52.76
                    )

                [5] => Array
                    (
                        [0] => 1950
                        [1] => 53.22
                    )

                [6] => Array
                    (
                        [0] => 1996
                        [1] => 53.41
                    )

                [7] => Array
                    (
                        [0] => 1880
                        [1] => 54.67
                    )

                [8] => Array
                    (
                        [0] => 1990
                        [1] => 57.58
                    )

                [9] => Array
                    (
                        [0] => 2011
                        [1] => 73.28
                    )

            )