Find max and min key in associative array

I have associative array like

array
{
    [company 1]=>array
                      (
                        [1981] => 1
                        [1945] => 3
                      )
   [company 2]=>array
                    (
                       [1990] => 18
                       [2005] => 13
                    )
   [company 3]=>array
                    (
                       [1950] => 6
                       [2012] => 9
                    )
}

I want to get lowest and highest key i.e. 1945 and 2012. How can i achieve this? I have already searched over stackoverflow and Hightest value of an associative array is the nearest possibility but it gives out min and max value and I want min and max key.

**I don’t want to use foreach loop **

Answer

If you really hate foreach, here’s a solution:

$arr = array(
  "Company 1" => array(
    "1981" => 1,
    "1945" => 3
  ),

  "Company 2" => array(
    "1990" => 18,
    "2005" => 13
  ),

  "Company 3" => array(
    "1950" => 6,
    "2012" => 9
  )
);


$arr = array_map("array_keys", $arr);
$arr = array_reduce($arr, "array_merge", array());

Your $arr would end up like this:

Array
(
    [0] => 1981
    [1] => 1945
    [2] => 1990
    [3] => 2005
    [4] => 1950
    [5] => 2012
)

Now you can use min() and max() functions or sort() it get the highest and lowest value easily.

sort($arr);
echo end($arr); /*highest value; actual output: 2012*/
echo reset($arr); /*lowest value; actual output: 1945*/