Recursively merge two associative 2d arrays

How can I merge one array inside another 2d array based on a unique value that is shared on both 2d array?

Arrays:

$arr1 = [
    "First" =>[
        "Name" => "John",
        "Id" => 123
    ],
    "Second" =>[
        "Name" => "Peter",
        "Id" => 45
    ]
];  

$arr2 = [
    "First" =>[
        "Age" => 34,
        "Id" => 123
    ],
    "Second" =>[
        "Age" => 24,
        "Id" => 45
    ]
];

$n = array_merge($arr1, $arr2);

Current output when var_dump $n:

array(2) {
 ["First"]=>
   array(2) {
    ["Age"]=>
    int(34)
    ["Id"]=>
    int(123)
 }
 ["Second"]=>
  array(2) {
    ["Age"]=>
    int(24)
    ["Id"]=>
    int(45)
 }
}

Desired output:

array(2) {
 ["First"]=>
   array(2) {
    ["Name"]=>
    String("John")
    ["Age"]=>
    int(34)
    ["Id"]=>
    int(123)
 }
 ["Second"]=>
  array(2) {
    ["Name"]=>
    String("Peter")
    ["Age"]=>
    int(24)
    ["Id"]=>
    int(45)
 }
}

Of course just by merging the two arrays wont fix my issue, but I was just wondering what approach I should take to do this.

Assuming this structure of your arrays, you can use array_replace_recursive.

$n = array_replace_recursive($arr1, $arr2);

Fiddle: https://3v4l.org/IPGsl

Some people can say that you can use array_merge_recursive, but no. As you have same key (Id) in both arrays, resulting array will have not the structure you expect. But in case you have different keys in both arrays - array_merge_recursive is an option too.