PHP array sort / multi_sort usort

Question

I need to sort this array by distance

Array
(
    [0] => Array
        (
            [name] => Pyro Pizza
            [distance] => 2.3
        )

    [1] => Array
        (
            [name] => Sparky's Pizza
            [distance] => 2.1
        )

    [2] => Array
        (
            [name] => American Dream Pizza - Portland
            [distance] => 0.5
        )

    [3] => Array
        (
            [name] => Ken's Artisan Pizza
            [distance] => 1.1
        )

    [4] => Array
        (
            [name] => Sparky's Pizza - SE
            [distance] => 2.2
        )

    [5] => Array
        (
            [name] => Vincente's Gourmet Pizza and the V-Room
            [distance] => 2
        )

    [6] => Array
        (
            [name] => Blind Onion Pizza and Pub
            [distance] => 0.6
        )

    [7] => Array
        (
            [name] => Hot Lips Pizza
            [distance] => 1.9
        )

    [8] => Array
        (
            [name] => Flying Pie Pizzeria
            [distance] => 2
        )

    [9] => Array
        (
            [name] => Hammy's Pizza
            [distance] => 2.4
        )

)

I used this..

usort($results, 'sortByOrder');

with this..

function sortByOrder($a, $b) {
    return $a['distance'] - $b['distance'];
}

but it doesn't work

Jeroen · Accepted Answer · 2011-05-16 15:53:25Z

3

This should do the job:

function sortByOrder($a, $b) {
    if ( $a ['distance'] == $b ['distance'] ) return 0;
    return ( $a ['distance'] < $b ['distance'] ) ? -1 : 1;
}

usort ( $results, 'sortByOrder' );

The problem with your code is that the comparison function, sortByOrder here, should return either 0 if they are equal or -1/1 if one of them is bigger. Your function however returned the difference in distance, which usort() can't parse.

answered May 16, 2011 at 15:53

Jeroen

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Comments

zaf · Accepted Answer · 2011-05-16 15:45:51Z

3

Your sortByOrder function doesn't look quite right.

From usort

The comparison function must return an integer less than, equal to, or greater than zero if the first argument is considered to be respectively less than, equal to, or greater than the second.

answered May 16, 2011 at 15:45

zaf

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4 Comments

zaf Over a year ago

@Kirk Strobec "Give a man a fish; you have fed him for today. Teach a man to fish; and you have fed him for a lifetime"

Kirk Strobeck Over a year ago

Concepts and syntax are two different worlds — In your analogy what you did is said "go get fish" as opposed to "go to the north shore with X net and Y boat at Z hour with A bait"

zaf Over a year ago

@Kirk Strobeck "Thanks man but I cannot figure out the function description or the several examples given on php.net - I would appreciate if you could expand some more. Cheers!"

Kirk Strobeck Over a year ago

I dont understand it either, thats why I posted the question, see the answer to learn more ;)

Andrew Makarenko · Accepted Answer · 2011-05-16 15:53:04Z

2

    function sortByOrder($a, $b) {
        if ($a['distance'] == $b['distance']) return 0; 
        return ($a['distance'] < $b['distance']) ? -1 : 1;
    }

answered May 16, 2011 at 15:53

Andrew Makarenko

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