Sort multidimensional array by multiple keys

Question

I'm trying to sort a multidimensional array by multiple keys, and I have no idea where to start. I looked at uasort, but wasn't quite sure how to write a function for what I need.

I need to sort by the state, then event_type, then date.

My array looks like this:

    Array
(
    [0] => Array
        (
            [ID] => 1
            [title] => Boring Meeting
            [date_start] => 2010-07-30
            [time_start] => 06:45:PM
            [time_end] => 
            [state] => new-york
            [event_type] => meeting
        )

    [1] => Array
        (
            [ID] => 2
            [title] => Find My Stapler
            [date_start] => 2010-07-22
            [time_start] => 10:45:AM
            [time_end] => 
            [state] => new-york
            [event_type] => meeting
        )

    [2] => Array
        (
            [ID] => 3
            [title] => Mario Party
            [date_start] => 2010-07-22
            [time_start] => 02:30:PM
            [time_end] => 07:15:PM
            [state] => new-york
            [event_type] => party
        )

    [3] => Array
        (
            [ID] => 4
            [title] => Duct Tape Party
            [date_start] => 2010-07-28
            [time_start] => 01:00:PM
            [time_end] => 
            [state] => california
            [event_type] => party
        )
...... etc

Answer 1

You need array_multisort

$mylist = array(
    array('ID' => 1, 'title' => 'Boring Meeting', 'event_type' => 'meeting'),
    array('ID' => 2, 'title' => 'Find My Stapler', 'event_type' => 'meeting'),
    array('ID' => 3, 'title' => 'Mario Party', 'event_type' => 'party'),
    array('ID' => 4, 'title' => 'Duct Tape Party', 'event_type' => 'party')
);

# get a list of sort columns and their data to pass to array_multisort
$sort = array();
foreach($mylist as $k=>$v) {
    $sort['title'][$k] = $v['title'];
    $sort['event_type'][$k] = $v['event_type'];
}
# sort by event_type desc and then title asc
array_multisort($sort['event_type'], SORT_DESC, $sort['title'], SORT_ASC, $mylist);

Answer 2

class Sort {
    private $actual_order = 'asc';
    private $actual_field = null;

    public function compare_arrays($array1, $array2) {

        if ($array1[$this->actual_field] == $array2[$this->actual_field]) {
            return 0;
        }
        elseif ($array1[$this->actual_field] > $array2[$this->actual_field]) {
            return ($this->actual_order == 'asc' ? 1 : -1);
        }
        else {
            return ($this->actual_order == 'asc' ? -1 : 1);
        }

    }


    public function order_array(&$array) {

        usort($array, array($this, 'compare_arrays'));

    }


    public function __construct ($field, $actual_order = 'asc') {
        $this->actual_field = $field;
        $this->actual_order = $actual_order;
    }

}

// use

$sort = new Sort ("state");

$sort->order_array($array);

Answer 3

With usort you can do it. The cmp_function should look like this.

function my_sorter($a, $b) {
    $c = strcmp($a['state'], $b['state']);

    if($c == 0) {
        $c = strcmp($a['event_type'], $b['event_type']);

        if($c == 0) {
            return strcmp($a['date_start'], $b['date_start']);
        } else {
            return $c;
        }
    } else {
        return $c;
    } }