Sort Array of MultiDiminsional Arrays on More Than One “Column” (Key) With Specified Sort Options

Question

I'm looking to be able to sort an array of multi-dimensional 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 what is similar the result of a DB query, but doesn't actually come from one, therefore the need to sort it in PHP rather than SQL.

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

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

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

    [3] => Array
        (
            [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;
        }
    };
}

Answer 2

In PHP 5.3 every parameter in the array has to be a reference when calling array_multisort() with call_user_func_array().

This function sorts a multidimensional array and shows a way to build an array of referenced params that works correctly.

function msort()
{
  $params = func_get_args();
  $array = array_pop($params);

  if (!is_array($array))
    return false;

  $multisort_params = array();
  foreach ($params as $i => $param) 
  {
    if (is_string($param)) 
    {
      ${"param_$i"} = array();
      foreach ($array as $index => $row) 
      {
        ${"param_$i"}[$index] = $row[$param];
      }
    }
    else 
      ${"param_$i"} = $params[$i];

    $multisort_params[] = &${"param_$i"};
  }
  $multisort_params[] = &$array; 

  call_user_func_array("array_multisort", $multisort_params);

  return $array;
}

Example:

$data is the given array from the question

$sorted_data = msort('city', SORT_ASC, SORT_STRING, 'zip', SORT_DESC, SORT_NUMERIC, $data)

Answer 3

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.

Answer 4

You might want to try using usort. All you have to do is make a functions that tell the sorter how to sort it. The docs have more info on how to do that.