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

Here is what I finally settled on for being able to sort multi-dimensional arrays. Both of the answers above are good but I was also looking for something flexible.

I definitely don’t think there is any one “right” answer, but this is what works for my needs and is flexible.

As you can see from my @link in the comment of _usortByMultipleKeys() it was adapted from a comment in the PHP manual that currently doesn’t seem to exist, but I believe http://www.php.net/manual/en/function.usort.php#104398 is a new version of the original comment. I have not explored using that new suggestion.

/**
 * Sort the resultSet.
 *
 * Usage: $sortOptions = array(
 *          'section', // Defaults to SORT_ASC
 *          'row' => SORT_DESC,
 *          'retail_price' => SORT_ASC);
 *        $results->sortResults($sortOptions);
 *
 * @param array $sortOptions    An array of sorting instructions
 */
public function sortResults(array $sortOptions)
{
    usort($this->_results, $this->_usortByMultipleKeys($sortOptions));
}


/**
 * Used by sortResults()
 *
 * @link http://www.php.net/manual/en/function.usort.php#103722
 */
protected function _usortByMultipleKeys($key, $direction=SORT_ASC)
{
    $sortFlags = array(SORT_ASC, SORT_DESC);
    if (!in_array($direction, $sortFlags)) {
        throw new InvalidArgumentException('Sort flag only accepts SORT_ASC or SORT_DESC');
    }
    return function($a, $b) use ($key, $direction, $sortFlags) {
        if (!is_array($key)) { //just one key and sort direction
            if (!isset($a->$key) || !isset($b->$key)) {
                throw new Exception('Attempting to sort on non-existent keys');
            }
            if ($a->$key == $b->$key) {
                return 0;
            }
            return ($direction==SORT_ASC xor $a->$key < $b->$key) ? 1 : -1;
        } else { //using multiple keys for sort and sub-sort
            foreach ($key as $subKey => $subAsc) {
                //array can come as 'sort_key'=>SORT_ASC|SORT_DESC or just 'sort_key', so need to detect which
                if (!in_array($subAsc, $sortFlags)) {
                    $subKey = $subAsc;
                    $subAsc = $direction;
                }
                //just like above, except 'continue' in place of return 0
                if (!isset($a->$subKey) || !isset($b->$subKey)) {
                    throw new Exception('Attempting to sort on non-existent keys');
                }
                if ($a->$subKey == $b->$subKey) {
                    continue;
                }
                return ($subAsc==SORT_ASC xor $a->$subKey < $b->$subKey) ? 1 : -1;
            }
            return 0;
        }
    };
}