PHP - sort hash array by key length

Question

I\'ve found a few answers to sorting by value, but not key.

What I\'d like to do is a reverse sort, so with:

    $nametocode[\'reallylongname\']=\'12         


        

Answer 1

You can use a user defined key sort function as a callback for uksort:

function cmp($a, $b)
{
    if (strlen($a) == strlen($b))
        return 0;
    if (strlen($a) > strlen($b))
        return 1;
    return -1;
}

uksort($nametocode, "cmp");

foreach ($nametocode as $key => $value) {
    echo "$key: $value\n";
}

Quick note - to reverse the sort simply switch "1" and "-1".

Answer 2

I have benchmarked some of sorting algorithms since performance is important for my project - here's what I've found (averaged result ran 1000x, sorted field had cca 300 elements with key size 3-50 chars):

• 2.01 sec ... uksort with anonymous create_function (by cojam)
• 0.28 sec ... array_multisort (by Gumbo)
• 2.69 sec ... uksort with non-anonymous function (by Colin Herbert) - surprise for me,
• 0.15 sec ... simple foreach + arsort

Sometime simple foreach still wins. Using dynamic PHP features has some performance penalty, obviously.

Answer 3

In PHP7+ you can use uksort() with spaceship operator and anonymous function like this:

uksort($array, function($a, $b) {
    return strlen($b) <=> strlen($a);
});

Answer 4

A simple problem requires a simple solution ;-)

arsort($nametocode, SORT_NUMERIC);
$result = array_keys($nametocode);

Answer 5

Behold my powerful inline methodologies. Preserve global space for the generations to come!

uksort($data, create_function('$a,$b', 'return strlen($a) < strlen($b);'));