Overwrite row data in a 2d array when related data is found in another 2d array

I have

Array_A ( [0] => Array ( [DATE] => 2012-11-28 , [totalCount] => )
          [1] => Array ( [DATE] => 2012-11-29 , [totalCount] => )
          [2] => Array ( [DATE] => 2012-11-30 , [totalCount] => ) )

Array_B ( [10] => Array ( [DATE] => 2012-11-28 , [totalCount] => 30 )
          [11] => Array ( [DATE] => 2012-11-30 , [totalCount] => 40 )
          [12] => Array ( [DATE] => 2012-12-05 , [totalCount] => 50 ) )

How to I do if I need to replace the Array_A with the values from the Array_B and the output should be

Array_A ( [0] => Array ( [DATE] => 2012-11-28 , [totalCount] => 30 )
          [1] => Array ( [DATE] => 2012-11-29 , [totalCount] =>    )
          [2] => Array ( [DATE] => 2012-11-30 , [totalCount] => 40 ) )

I just noticed the part where you only want the keys from array_a to be used, this loop wil do.

foreach($array_a as $key => $value){
    if (array_key_exists($key, $array_b){
        $result[$key] = $array_b[$key]; 
    } else {
        $result[$key] = null;
    }
}

Or, if you want the value of array_a being used if the key in array_b does not exist, simply replace the statement in the else-clause to: $result[$key] = $value;.

• http://php.net/manual/en/function.array-key-exists.php
• http://php.net/manual/en/control-structures.foreach.php
• http://php.net/manual/en/control-structures.if.php

Edit (because of the comment of mickmackusa)

I think I misread the question back in the day and was expecting the key of the second array to be unique (like an identiefier in a table). So I was expecting array_b to be something like:

$array_b = [
    0 => ['DATE' => '2012-11-28', 'totalCount' => 30],
    2 => ['DATE' => '2012-11-30', 'totalCount' => 40],
    12 => ['DATE' => '2012-12-05', 'totalCount' => 50],
];

In that case the earlier mentioned code will work. Demo

See the answer from mickmackusa as that actually solves the issue of the OP.