ACF: Updating gallery field doesn't work in backend

Question

I have tried to update a gallery field and the images shows up in frontend but not the backend.

// I have also tried to use the ACF field name like $field = 'field_xxxxxxxxxxxxx';

$field = 'images';

$post_id = 12345;

$attachments_ids = [
    0 => 22222,
    1 => 33333,
    2 => 44444,
    3 => 55555
];

update_field($field, $attachment_ids, $post_id);

Answer 1

I'm assuming that $attachments_ids are the new values you want to save.

$field = get_field('images');

$attachments_ids = [
    0 => 22222,
    1 => 33333,
    2 => 44444,
    3 => 55555
];

update_field($field, $attachment_ids, $post_id);

Answer 2

I ran into this issue also. This worked for me:

1. It only seems to work if using the field_xxxx syntax for the selector.
2. The array of attachment IDs should be flat, with no index key.

    $field = 'field_xxxxxxxxxxxxx';

    $post_id = 12345;

    $attachments_ids = [
        22222,
        33333,
        44444,
        55555
    ];

    update_field($field, $attachment_ids, $post_id);