How to sort array by filesize strings?

Question

I am trying to figure out how to sort an array by filesize strings correctly. I am building an array like the one shown below and would like to sort it by the filesize column. I have looked around but havent been able to find anything that has been too helpful in sorting it.

Array (
    [0] => Array (
        [0] => FileName 
        [1] => 71.6 MB 
        [2] => /path/to/file/
        [3] => 2018-12-08 19:31:17 ) 
    [1] => Array ( 
        [0] => FileName
        [1] => 1.15 GB 
        [2] => /path/to/file/
        [3] => 2018-12-08 17:36:28 ) 
    [2] => Array ( 
        [0] => FileName
        [1] => 10.22 MB 
        [2] => /path/to/file/
        [3] => 2018-12-08 16:13:24 ) 
    [3] => Array ( 
        [0] => FileName
        [1] => 34.42 MB 
        [2] => /path/to/file/
        [3] => 2018-12-08 16:24:27 ) 
    [4] => Array ( 
        [0] => FileName
        [1] => 466.18 KB 
        [2] => /path/to/file/
        [3] => 2018-12-08 16:31:44 ) 
    [5] => Array ( 
        [0] => FileName
        [1] => 26.98 MB 
        [2] => /path/to/file/
        [3] => 2018-12-08 17:34:57 )
    )

I am loading data from a database and I get and add the file sizes while building the array using this function.

function format_size($size) {
    $sizes = array(" Bytes", " KB", " MB", " GB", " TB", " PB", " EB", " ZB", " YB");
    if ($size == 0) { return('n/a'); } else {
    return (round($size/pow(1024, ($i = floor(log($size, 1024)))), 2) . $sizes[$i]); }
}

This is basically how I am building the array.

if ($stmt->rowCount() > 0) {
    $stmt->setFetchMode(PDO::FETCH_ASSOC);
    $iterator = new IteratorIterator($stmt);
    $data_array = Array();
    foreach ($iterator as $key => $row) {
        $fname = $row["filename"];
        $size = filesize('/path/to/file/' . $row["filename"]);
        $fsize = format_size($size);
        $fpath = '/path/to/file/' . $row["filename"];
        $f_tstamp = $row['timestamp'];

        $file_array = Array(
            $fname,
            $fsize,
            $fpath,
            $f_tstamp
            );

        $time[$key] = $row['timestamp'];
        $data_array[] = $file_array;
   }

This is how I sort by timestamps.

array_multisort($time, SORT_DESC, $data_array);
foreach ($data_array as $val) {
    print $val[0];
    print $val[1];
    print $val[2];
    print $val[3];
}

What can I do to sort it properly using the filesize strings? Thanks.

Answer 1

In order to make sorting easier, you should store the numeric value returned by filesize inside the array, e.g. by adding it to the end like so:

$file_array = Array(
    $fname,
    $fsize,
    $fpath,
    $f_tstamp,
    $size
);

Then, it should be as simple as

usort($data_array, function($a, $b){ return $a[4] - $b[4]; });

The second parameter of usort is what's known as a comparator function in most languages. It receives two items of your array at a time, and expects an integer return value:

• 0 means keep the elements in the order they are currently in
• a negative value means $a is less than $b, so it should come before it
• a positive value means $a is greater than $b, so it should come after it

The fourth index of each argument is your size value, and by subtracting the first from the second you will get an ascending sort order. You can reverse the operands ($b[4] - $a[4]) to get a descending sort order.

If you use PHP 7+ you can also use the spaceship operator here instead.

Answer 2

You need to use php usort, Take a look at php.net usort

It takes a comparator function as second argument