Count number of non-null values in each column of a 2d array

Let's say I have an array:

[
  {0:1, 1:5, 3:null},
  {0:4, 1:null, 3:null},
  {0:null, 1:5, 3:5}
]

I want to count non-null values per associative key so that my expected output is:

[{0:2, 1:2, 3:1}]

Try this it will find the sum even if one key exists in only one array as well. This will find both the sum and the counts.

<?php

$arr = [
  [0 => 1, 1 => 5, 3 => null],
  [0 => 4, 1 => null, 3 => null],
  [0 => null, 1 => 5, 3 => 5]
];
$out   = [];
$count = [];
foreach ( $arr as $key => $value) {
    # code...
    foreach ( $value as $k => $v) {
      if(NULL != $v) {
         $count[$k] = isset($count[$k]) ? ($count[$k] + 1) : 1;
      }

      $v       = (NULL === $v) ? 0 : $v;
      $out[$k] = isset($out[$k]) ? ($out[$k] + $v) : $v;

   }

}
echo '<pre>';
echo "Sum array is : ";
print_r($out);
echo '</pre>';

echo '<pre>';
echo "Count array is : ";
print_r($count);
echo '</pre>';

Will gives the output

Sum array is : 
Array
(
    [0] => 5
    [1] => 10
    [3] => 5
)

Count array is : 
Array
(
    [0] => 2
    [1] => 2
    [3] => 1
)

And for the input array commented below

    $arr = [ 
    [0 => null, 1 => null, 3 => null], 
    [0 => 4, 1 => null, 3 => null], 
    [0 => null, 1 => 5, 3 => 5] 
];

Will give

Sum array is : 
Array
(
    [0] => 4
    [1] => 5
    [3] => 5
)

Count array is : 
Array
(
    [0] => 1
    [1] => 1
    [3] => 1
)

If this is not what you want give the expected output for the commented array as well.