php firebase api - delete children element from nested document

Question

I'm using php sdk to delete some fields from firestore database, i want to delete a map from an array inside a document, but instead the function used delete all maps inside the parent array.

My firestore database looks like this

What i'm trying to do is remove a specific index ex: index 0 with it's children from imageUrls array not all the maps inside it.

I tried these 2 functions :

$usersRef->update([
        ['path' => 'imageUrls.image_url', 'value' => FieldValue::arrayRemove(['image.png'])]
    ]);

and this one

$usersRef->update([
    ['path' => 'imageUrls.image_url', 'value' => FieldValue::deleteField()]
]);

The first function remove all imageUrls childrens and change imageUrls type from array to map, while the second one nothing happened. All the fields still exist in the document and no deletion occurd

<?php 

namespace App\Services;
use Google\Cloud\Firestore\FirestoreClient;
use Google\Cloud\Firestore\FieldValue;
use Google\Cloud\Firestore\FieldPath;

class FirebaseService
{
    public function delete()
    {
        // Create the Cloud Firestore client
        $db = new FirestoreClient(
            ['projectId' => 'MyProjectId']
        );

        $usersRef = $db->collection('NewStories')->document('1');

        $usersRef->update(
                         [
                              ['path' =>'imageUrls.image_url', 
                              'value' => FieldValue::arrayRemove(['image.png'])]
                         ]);  
    }
}

Answer 1

This can be achieved using the arrayRemove() method. As the PHP Client for Firestore says

Returns a special value that can be used with set(), create() or update() that tells the server to remove the given elements from any array value that already exists on the server. All instances of each element specified will be removed from the array. If the field being modified is not already an array it will be overwritten with an empty array.

---

Update:

Firebase does not support updating an existing element in an indexed array. More information can be found in the Official Documentation.

Workaround:

Reading the entire array out of the document, make modifications to it in memory, then update the modified array field entirely.**

Credits to this Firestore Update single item in an array field case.