Sort array of associative arrays on multiple columns using specified sorting rules

Question

I'm looking to be able to sort an array of associative arrays on more than one column. To further complicate it, I'd like to be able to set specific sort options per key/column. I have a set of data that is similar to a db query's result set, but it doesn't actually come from one so I need to sort it in PHP rather than SQL.

[
    ['first_name' => 'Homer', 'last_name' => 'Simpson', 'city' => 'Springfield', 'state' => 'Unknown', 'zip' => '66735'],
    ['first_name' => 'Patty', 'last_name' => 'Bouvier', 'city' => 'Scottsdale', 'state' => 'Arizona', 'zip' => '85250'],
    ['first_name' => 'Moe', 'last_name' => 'Szyslak', 'city' => 'Scottsdale', 'state' => 'Arizona', 'zip' => '85255'],
    ['first_name' => 'Nick', 'last_name' => 'Riviera', 'city' => 'Scottsdale', 'state' => 'Arizona', 'zip' => '85255'],
];

I would like to be able to sort it similar to what could be done with a DB query. Oh, and sometimes a column/key needs to be specified by number.

What I had in mind was something similar to this:

$sortOptions = array(
    array( 'city', SORT_ASC, SORT_STRING),
    array( 'zip', SORT_DESC, SORT_NUMERIC),
    array( 2, SORT_ASC, SORT_STRING) // 2='last_name'
);
$sorter = new MultiSort($data, $sortOptions);
$sortedData = $sorter->getSortedArray();
print_r($jmsSorted);

What I would like to end up with is this:

Array
(
    [0] => Array
        (
            [first_name] => Nick
            [last_name] => Riviera
            [city] => Scottsdale
            [state] => Arizona
            [zip] => 85255
        )

    [1] => Array
        (
            [first_name] => Moe
            [last_name] => Szyslak
            [city] => Scottsdale
            [state] => Arizona
            [zip] => 85255
        )

    [2] => Array
        (
            [first_name] => Patty
            [last_name] => Bouvier
            [city] => Scottsdale
            [state] => Arizona
            [zip] => 85250
        )

    [3] => Array
        (
            [first_name] => Homer
            [last_name] => Simpson
            [city] => Springfield
            [state] => Unknown
            [zip] => 66735
        )

)

UPDATE: I think that ideally, a solution would result in dynamically creating

array_multisort( $city, SORT_ASC, SORT_STRING, $zip, SORT_DESC, SORT_NUMERIC, $last_name, SORT_ASC, SORT_STRING, $inputArray);

The problem is that I don't want to have to "hard code" those key names in there. I tried creating a solution based upon Example #3 Sorting database results from the array_multisort() documentation that ended up using array_multisort() but I cannot seem to find a way to use my dynamically built argument list for array_multisort().

My attempt was to "chain" those arguments together into an array and then

call_user_func_array( 'array_multisort', $functionArgs);

That results in an

Warning: Parameter 2 to array_multisort() expected to be a reference, value given in...

Answer 1

This should work for the situation you describe.

usort($arrayToSort, "sortCustom");

function sortCustom($a, $b)
{
    $cityComp = strcmp($a['city'],$b['city']);
    if($cityComp == 0)
    {
        //Cities are equal.  Compare zips.
        $zipComp = strcmp($a['zip'],$b['zip']);
        if($zipComp == 0)
        {
            //Zips are equal.  Compare last names.
            return strcmp($a['last_name'],$b['last_name']);
        }
        else
        {
            //Zips are not equal.  Return the difference.
            return $zipComp;
        }
    }
    else
    {
        //Cities are not equal.  Return the difference.
        return $cityComp;
    }
}

You could condense it into one line like so:

function sortCustom($a, $b)
{
    return ($cityComp = strcmp($a['city'],$b['city']) ? $cityComp : ($zipComp = strcmp($a['zip'],$b['zip']) ? $zipComp : strcmp($a['last_name'],$b['last_name'])));
}

As far as having a customizable sort function, you're reinventing the wheel. Take a look at the array_multisort() function.