如何向多维数组添加一个维度？

I have a multi-dimensional array that looks like this:

Array
(
  [Category-1-Name] => Array      // Category-array
  (
    [0] => Array                  // Post-array
      (
        [0] => Post-0-name
        [1] => Post-0-url
        [2] => Post-0-text
      )

    [1] => Array
      (
        [0] => Post-1-name
        [1] => Post-1-url
        [2] => Post-1-text
      )
  )

  [Category-2-Name] => Array
  (
    [0] => Array
      (
        [0] => Post-0-name
        [1] => Post-0-url
        [2] => Post-0-text
      )

    [1] => Array
      (
        [0] => Post-1-name
        [1] => Post-1-url
        [2] => Post-1-text
      )
  )
)

I fill the array like this:

$q = array();
$a = array("Post-0-name", "Post-0-url", "Post-0-text");
foreach ( $categories as $key=>$category ) {
  $b = $category->name;
}
$q[$b][] = $a;

I would like to add one more dimension: Category description for each category.

Is it posibble to do this without repeating the description in every Post-array?

Yes, it's possible. I think the optimal way will be to create array of this kind:

[Category-1-Name] => Array      // Category-array
(
  [descripion] => 'some description here'
  [posts] => Array
    [0] => Array                  // Post-array
      (
        [0] => Post-0-name
        [1] => Post-0-url
        [2] => Post-0-text
      )