Explanation of an Example of php Two dimensional Array Sorting by a Certain Key Value

Before sorting

Array
(
  [0] => Array
    (
      [name] =>  Dragon 
      [age] => 2017-02-28
    )
  [1] => Array
    (
      [name] =>  Dragon 2
      [age] => 2017-03-14
    )
  [2] => Array
    (
      [name] =>  Small 3
      [age] => 2017-05-09
    )
  [3] => Array
    (
      [name] =>  Dragon 4
      [age] => 2017-02-03
    )
  [4] => Array
    (
      [name] =>  Dragon 5
      [age] => 2017-03-23
    )
  [5] => Array
    (
      [name] =>  Dragon 6
      [age] => 21
    )
)
array_multisort(array_column($arr,'age'),SORT_DESC,$arr);
print_r($arr);

After sorting

Array
(
  [0] => Array
    (
      [name] =>  Dragon 6
      [age] => 21
    )
  [1] => Array
    (
      [name] =>  Small 3
      [age] => 2017-05-09
    )
  [2] => Array
    (
      [name] =>  Dragon 5
      [age] => 2017-03-23
    )
  [3] => Array
    (
      [name] =>  Dragon 2
      [age] => 2017-03-14
    )
  [4] => Array
    (
      [name] =>  Dragon 
      [age] => 2017-02-28
    )
  [5] => Array
    (
      [name] =>  Dragon 4
      [age] => 2017-02-03
    )
)

Among them, array_column (array, a key value in the array) takes out a column of a key value from the multidimensional array and returns a 1-dimensional array;

array_multisort (array (1-dimensional array), sort (SOTR_ASC, SOTR_DESC), other arrays (can be 2-dimensional))

Summarize