php sort array by amount of items?

Question

I have a multi-dimension array of australian states, and inside each state there are items. I was wondering if it were possible to reorder an array so the states with the most amount of items are displayed first?

Here's my array, any help would be appreciated :)

alex · Accepted Answer · 2011-04-01 00:48:25Z

3

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

Assuming >= PHP 5.3

edited Apr 1, 2011 at 0:48

answered Mar 31, 2011 at 23:27

alex

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2 Comments

jrn.ak Over a year ago

shouldn't there be an array variable in there somewhere?

alex Over a year ago

@jnpcl Whoops. First post from an iPad, I was bound to stuff something up :)

Mike Lewis · Accepted Answer · 2011-03-31 23:42:24Z

1

After running this, $arr will now be sorted from highest populated elements to lower.

function cmpArray($a, $b)
{
    $countA = count($a);
    $countB = count($b);
    if ($countA == $countB) {
        return 0;
    }
    return ($countA < $countB) ? 1 : -1;
}

uasort($arr, "cmpArray");

edited Mar 31, 2011 at 23:42

answered Mar 31, 2011 at 23:31

Mike Lewis

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4 Comments

jrn.ak Over a year ago

Seems a waste to assign variables.

Mike Lewis Over a year ago

Not true at all. Caching the result of the count() will make it so we don't have to recalculate count() every time we want it.

SoulieBaby Over a year ago

Is there any way of keeping the initial array keys? (VIC, ACT etc)

alex Over a year ago

@Mike won't they be deallocated anyway when the function returns?

jrn.ak · Accepted Answer · 2011-03-31 23:43:50Z

Similar to @alex's answer, but without the anonymous function (so it works on PHP <5.3)

<?php
    $array = array(
        'three' => array(
            'one',
            'two',
            'three'
        ),
        'one' => array(
            'one'
        ),
        'two' => array(
            'one',
            'two'
        ),
    );

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

    uasort($array, 'csort');

    print_r($array);
?>

Output:

Array
(
    [one] => Array
        (
            [0] => one
        )

    [two] => Array
        (
            [0] => one
            [1] => two
        )

    [three] => Array
        (
            [0] => one
            [1] => two
            [2] => three
        )

)

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