在PHP中根据长度对多维数组进行排序

Question

I have a function that finds all the possible combinations of an array:

function combination($array) 
{    
    $results = array(array());

    foreach ($array as $element)
        foreach ($results as $combination)
            array_push($results, array_merge(array($element), $combination));

    return $results;
}

This returns a multidimensional array and it works.

If I try to print the array, I use this:

foreach (combination($set)  as $combination)
{
    print join("\t", $combination) . "  - ";
}

For: $set = array('s','f','g');

The output is: - s - f - fs - g - gs - gf - gfs -

Now what I cant figure out is how can I sort the combinations according to length in a way where the output becomes: - gfs - gs - gf - fs - g - s - f -

Answer 1

you need to use 'usort' for this:

function sortByLength($a, $b) {
    return count($b) - count($a);
}

$result = combination($set);

usort($result, 'sortByLength');

you could also just use 'sortByLength' as an anonymous function, instead of defining it, if you use this only once:

$result = combination($set);

usort($result, function($a, $b) {
    return count($b) - count($a);
} );