buildUniqueId(string $hook, string|array $function, integer|boolean $priority) : string
Build Unique ID for storage and retrieval.
Simply using a function name is not enough, as several functions can have the same name when they are enclosed in classes.
Used for creating unique id
Used in counting how many hooks were applied. If === false and $function is an object reference, we return the unique id only if it already has one, false otherwise.
unique ID for usage as array key