how to array_push a string into a multidimensional array

Question

Here is the problem:

  $arr = array(array());

  $arr[0]['a'] = 'for 0.a';
  $arr[0]['b'] = 'for 0.b';
  $arr[1]['a'] = 'for 1.a';
  $arr[1]['b'] = 'for 1.b';

  array_push($arr,'for 2.a');
  array_push($arr,'for 2.b');

  print_r($arr);

String "for 2.a" should be in $arr[2]['a']. How can I do?

Answer 1

array_push($arr,array('a'=>'for 2.a','b'=>'for 2.b'));

or

$arr[2]['a'] = 'for 2.a';
$arr[2]['b'] = 'for 2.b';