I'm creating a custom JSON:API Resource to store push notifications tokens.

The user account field where the tokens are stored has a limit of 5 items.

I am using appendItem() to add the value to field.

However, if the field already has 5 values, then appendItem() does nothing. In this case, instead of doing nothing, I want to bump the first item (the value saved first) from the array and then move all the other values up a place (last in last out).

I can code this myself but it occurred to me that this may be something Drupal already provides but I just don't know enough about the API to figure out where to look for it. Does Drupal provide some way to handle multi-value field values when the limit on the number of values has been reached?

Here's my code so far:

// Make sure we have a real token.
if (strlen($push_token) >= 100) {

  // Generate an array of the existing token values.
  $existing_tokens = $current_user->get('field_text_token_push')->getValue();
  $token_values = [];
  foreach($existing_tokens as $existing_token) {
    $token_values[] = $existing_token['value'];

  // Check whether the token already exists.
  if (in_array($push_token, $token_values)) {
    $this->loggerFactory->notice("Push token: Did not add token for UID @uid because it already exists.", [
      '@uid' => $uid,
    $return_bool = TRUE;
  } else {
    // Add the token.
    // Todo: If we have reached the field limit, automatically remove the earliest value and replace with the new value.
    $this->loggerFactory->notice("Push token: Added token for UID @uid.", [
      '@uid' => $uid,
    $return_bool = TRUE;

2 Answers 2


Broken these down into separate lines to help you pick and choose what you need.

$field = $current_user->get('field_text_token_push');
$field_definition = $field->getFieldDefinition();
$field_storage_definition = $field_definition->getFieldStorageDefinition();

// Upper limit.
$cardinality = $field_storage_definition->getCardinality();

// Number of current items.
$items = $field->count();

I don't know about this but I suspect that there isn't anything or any method that will automatically handle your use case (e.g. FIFO for multi value fields). You will probably have to code it yourself with a combination of the above and...

I guess with this then you could $field->removeItem(0)->rekey() if you've reached the maximum cardinality. Obviously handling excluding count comparisons where the cardinality is FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED


It should be no problem to bump the first item with array_slice():

$values = $node->field_foo->getValue();
$values[] = ['value' => 'bar'];
$values = array_slice($values, -5);

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