更改数组/对象嵌套组合数组中的值时出现问题

I don't know what to do to get this done what would like to do. I tried multiple approaches, e.g. I used array_map, array_walk, nested foreach loops with get_object_vars and I worked with json_decode/encode and so on. I always come a little bit further but never reach my goal and I would like to get some guidance from you

Basically when you see the array below, how would you proceed when you want to change some value in the path array for multiple values in the array itself?

My questions:

1) Is it right that I must convert both nested objects to an array first or is this not nesessary to do this? I mean I always get some type conversion error which tells me that I either have everything as an object or array. Is this right?

2) If this mistery is solved, which php array function is the appropriate one to change values in an array(/object)? As I have written above, I tried so many and I don't see the trees in the woods anymore. Which one do you suggest to me to use in a foreach loop?

Array
(
    [0] => stdClass Object
        (
            [doc] => stdClass Object
                (
                    [path] => Array
                        (
                            [0] => Bob
                            [1] => pictures
                            [2] => food
                        )
                )

        )

    [1] => stdClass Object
        (
            [doc] => stdClass Object
                (

                    [path] => Array
                        (
                            [0] => Alice
                            [1] => pictures
                            [2] => vacations
                            [3] => rome
                        )
                )

        )
)

I would suggest that,

1. you create an array with keys as new path and value as old path ( path to be replaced).
2. Loop you path array and check if it is available in above defined array.
3. If available replace it with key of above defined array.

For example

// array defined as point 1
$change_path_array= array('pics'=>'pictures','meal'=>'food');
// $array is your array.
foreach ($array as $value) {
    // loop you path array  
    for($i=0;$i<count($value->doc->path);$i++){
        // check if the value is in defined array
        if(in_array($value->doc->path[$i],$change_path_array)){
            // get the key and replace it. 
            $value->doc->path[$i] = array_search($value->doc->path[$i], $change_path_array);
        }
    }
}

Out Put: picture is replaced with pics and food with meal

Array
(
    [0] => stdClass Object
        (
            [doc] => stdClass Object
                (
                    [path] => Array
                        (
                            [0] => Bob
                            [1] => pics
                            [2] => meal
                        )

                )

        )

    [1] => stdClass Object
        (
            [doc] => stdClass Object
                (
                    [path] => Array
                        (
                            [0] => Alice
                            [1] => pics
                            [2] => vacations
                            [3] => rome
                        )

                )

        )

)

You can modify the code to check casesensitive.

You can do it like this:

for($i = 0; $i < count($arr); $i++){
    $path_array = $arr[$i]->doc->path;
    // do your modifications for [i]th path element
    // in your case replace all 'Bob's with 'Joe's
    $path_array = array_map(function($paths){
        if($paths == 'Bob') return 'Joe';
        return $paths;
    }, $paths_array);

    $arr[$i]->doc->path = $path_array;
}

Example of changing all pictures to photos:

$doc1 = new \stdClass;
$doc1->doc = new \stdClass;
$doc1->doc->path = array('Bob', 'pictures', 'food');

$doc2 = new \stdClass;
$doc2->doc = new \stdClass;
$doc2->doc->path = array('Alice', 'pictures', 'vacations', 'rome');

$documents = array($doc1, $doc2);

/* change all 'pictures' to 'photos' */
foreach ($documents as &$doc) {
    foreach ($doc->doc->path as &$element) {
        if ($element == 'pictures') {
            $element = 'photos';
        }
        unset($element);
    }
    unset($doc);
}
print_r($documents);