How to extract data out of a specific PHP array

Question

I have a multi-dimensional array that looks like this: The base array is indexed based on category ids from my catalog.

$cat[category_id]

Ea

Answer 1

Assuming it's something of this sort:

$ary = Array(
  0 => Array(
    'parent_category_id' => null,
    'sort_order' => 0,
    'name' => 'my-category-name0'
  ),
  1 => Array(
    'parent_category_id' => 0,
    'sort_order' => 1,
    'name' => 'my-category-name1'
  ),
  2 => Array(
    'parent_category_id' => 0,
    'sort_order' => 2,
    'name' => 'my-category-name2'
  ),
  3 => Array(
    'parent_category_id' => null,
    'sort_order' => 0,
    'name' => 'my-category-name3'
  ),
  4 => Array(
    'parent_category_id' => 3,
    'sort_order' => 0,
    'name' => 'my-category-name4'
  )
);

You can use a combination of a foreach and usort to achieve what you're going for.

// @array: the array you're searchign through
// @parent_id: the parent id you're filtering by
function getFromParent($array, $parent_id){
  $result = Array();
  foreach ($array as $category_id => $entry){
    if ($entry['parent_category_id']===$parent_id)
      $result[$category_id] = $entry;
  }
  usort($result,create_function('$a,$b','return ($a["sort_order"]>$b["sort_order"]?1:($b["sort_order"]<$a["sort_order"]?-1:0));'));
  return $result;
}

var_export(getFromParent($ary,0));

EDIT Sorry, fixed some syntax errors. Tested, and works (at least to result in what I was intending)
EDITv2 Here's the raw output from the above:

array (
  0 => 
  array (
    'parent_category_id' => 0,
    'sort_order' => 1,
    'name' => 'my-category-name1',
  ),
  1 => 
  array (
    'parent_category_id' => 0,
    'sort_order' => 2,
    'name' => 'my-category-name2',
  ),
)

(Used var_export just for you @FelixKling)

EDITv3 I've updated my answer to go along with the OP's update. I also now make it retain the original "category_id" values in the result array.