getArity example

  public static function compare(ResourceIdentifier $a, ResourceIdentifier $b) {
    $result = strcmp(sprintf('%s:%s', $a->getTypeName(), $a->getId()), sprintf('%s:%s', $b->getTypeName(), $b->getId()));
    // If type and ID do not match, return their ordering.     if ($result !== 0) {
      return $result;
    }
    // If both $a and $b have an arity, then return the order by arity.     // Otherwise, they are considered equal.     return $a->hasArity() && $b->hasArity()
      ? $a->getArity() - $b->getArity()
      : 0;
  }

  /** * Deduplicates an array of ResourceIdentifier objects. * * @param \Drupal\jsonapi\JsonApiResource\ResourceIdentifier[] $resource_identifiers * The list of ResourceIdentifiers to deduplicate. * * @return \Drupal\jsonapi\JsonApiResource\ResourceIdentifier[] * A deduplicated array of ResourceIdentifier objects. * * @see self::isDuplicate() */