Array push problem

yes…you are right I am referring to a PHP array…despite the above form being in a JSON string.I do not understand though how array_replace() will help.Here is the PHP array(part of it):

array(3) {  ["sunday"]=>  array(4) {    ["open_a"]=>    NULL    ["close_a"]=>    NULL    ["open_b"]=>    NULL    ["close_b"]=>    NULL  }
  ....
  ["friday"]=>  array(4) { ["open_a"]=>string(8) "11:00:00",["close_a"]=>string(8) "12:30:00"["open_b"]=>
    NULL    ["close_b"]=>  NULL  }
  ["saturday"]=> array(4) { ["open_a"]=> NULL["close_a"]=> NULL["open_b"]=> NULL["close_b"]=>NULL
  }
}

Here is the second array:
array(2) { [0]=> string(6) "Friday" [1]=> string(8) "Saturday"}

probably it is my fault I did not said about this second array…
You see the goal here is add a holiday member(in the manner described to my first post) to first multiD array…in these members of it where the keys(which are weekdays) are in agreement with values of the second array.

For example as you see the second array contains Friday and Saturday and accordingly to these inner arrays in the multiD array must the holiday member must be added.

Sorry If I was not clear from the beginning