Changing multidimensional array key value having his keys in another array - php

Question

I have two arrays:
$array = [
'application' => [
'foo' => [
'bar' => 1
]
]
];
$array_2 = [
0 => 'application',
1 => 'foo',
2 => 'bar'
];
How can I change the value of the first array knowning that the last key in the second array is the key who's value must be changed in the first array?
As you can see the second array contains all the keys from the first array. I want to do something like:
$array[$array_2] = 2;
... I suppose I must create a for loop?
For example, if I want to change the bar key value, I must do:
$array['application']['foo']['bar'] = 2;
... but I don't know which key I must change, I only have an array containing keys, and the last key in the list is the key that's value must be changed.

Answer 1

You could build a recursive function, or use a reference:
$result =& $array;
foreach($array_2 as $key) {
$result =& $result[$key];
}
$result = 2;
print_r($array);

Answer 2

This will do it, although not sure what you are trying to achieve.
$array[$array_2[0]][$array_2[1]][$array_2[2]] = 2;

Answer 3

Recursively add the keys. This works -
function get_keys($arr, &$keys){
$keys = array_merge($keys,array_keys($arr));
foreach($arr as $a){
if(is_array($a)){
get_keys($a, $keys);
}
}
}
$array = Array(
'application' => Array(
'foo' => Array(
'bar' => 1
)
)
);
$keys = Array();
get_keys($array, $keys);
var_dump($keys);
OUTPUT-
array
0 => string 'application' (length=11)
1 => string 'foo' (length=3)
2 => string 'bar' (length=3)