通过数组集的键对多维数组进行排序

Question

I'm looking for a solution to sort by key a multi dimensional array, the point is that I can sort a set of array with multidimensional that has no custom key ID and the array is in set, but this array contains custom key and I need to sort by date:

My array is:

$newDataSet = array(
 '2017-02-03' => array(
  array(
    array(
     'name' => 'Paul',
     'state' => 'in',
     'date' => '2017-02-03'    
    ),
    array(
     'name' => 'Paul',
     'state' => 'out',
     'date' => '2017-02-03'    
    )
  )
 ),
'2017-01-02' => array(
  array(
    array(
     'name' => 'John',
     'state' => 'in',
     'date' => '2017-01-02'    
    ),
    array(
     'name' => 'John',
     'state' => 'out',
     'date' => '2017-01-02'    
    )
  )
 ),
'2017-04-01' => array(
  array(
    array(
     'name' => 'Smith',
     'state' => 'in',
     'date' => '2017-04-01'    
    ),
    array(
     'name' => 'Smith',
     'state' => 'out',
     'date' => '2017-04-01'    
    )
  )
 )
);

uasort($newDataSet, function($a, $b) { return($a['date'] - $b['date']); });

As I understand usort will sort only the array of the multidimensional, so in my case is wrong because I don't have the structure to use it, is there a way to order by key asc ? I mean by date asc ?

Any hint/documentation for better understanding is appreciated.

Expected result:

$newDataSet = array(
     '2017-01-02' => array(
      array(
        array(
         'name' => 'Paul',
         'state' => 'in',
         'date' => '2017-01-02'    
        ),
        array(
         'name' => 'Paul',
         'state' => 'out',
         'date' => '2017-01-02'    
        )
      )
     ),
    '2017-02-03' => array(
      array(
        array(
         'name' => 'John',
         'state' => 'in',
         'date' => '2017-02-03'    
        ),
        array(
         'name' => 'John',
         'state' => 'out',
         'date' => '2017-02-03'    
        )
      )
     ),
    '2017-04-01' => array(
      array(
        array(
         'name' => 'Smith',
         'state' => 'in',
         'date' => '2017-04-01'    
        ),
        array(
         'name' => 'Smith',
         'state' => 'out',
         'date' => '2017-04-01'    
        )
      )
     )
    );

Answer 1

you can use ksort(), live demo .

ksort($newDataSet);
print_r($newDataSet);