Sort a multi-dimensional array by the size of its sub-arrays

Question

I have this multidimensional array:

Array
(
    [0] => Array
        (
        [0] => 2012-02-26 07:15:00
        )
    [1] => Array
        (
              


        

Answer 1

It seems to me that all of the other answers are working too hard. usort(), count(), and foreach() aren't necessary and when I tried natsort() it gave me: Notice: Array to string conversion in [...][...].

rsort() will put the longest subarrays first.

Code:

$array=array(
    ["2012-02-26 18:55:00","2012-02-26 17:45:00"],
    ["2012-02-26 07:15:00"],
    ["2012-02-26 18:57:00","2012-02-26 17:45:00","2012-02-26 18:55:00"],
    ["2012-02-26 17:45:00","2012-02-26 18:55:00"]
);

$size=3; // modify this line to declare how many subarrays to capture
rsort($array); // sort the subarrays in DESC order
var_export(array_slice($array,0,$size));  // print the first n subarrays

Output:

array (
  0 => 
  array (
    0 => '2012-02-26 18:57:00',
    1 => '2012-02-26 17:45:00',
    2 => '2012-02-26 18:55:00',
  ),
  1 => 
  array (
    0 => '2012-02-26 18:55:00',
    1 => '2012-02-26 17:45:00',
  ),
  2 => 
  array (
    0 => '2012-02-26 17:45:00',
    1 => '2012-02-26 18:55:00',
  ),
)

If you want to implement some additional sorting to break the length-ties (like between your two 2-element subarrays), then you will need to specify that in your question.