elgg_echo($message_key, array $args=[], $language="")
Given a message key, returns an appropriately translated full-text string.
notify_user($to, $from=0, $subject= '', $message= '', array $params=[], $methods_override=null)
Notify a user via their preferences.
elgg_error_response($error= '', $forward_url=REFERRER, $status_code=ELGG_HTTP_OK)
Prepare an error response to be returned by a page or an action handler.
register_user($username, $password, $name, $email, $allow_multiple_emails=false, $subtype=null)
Registers a user, returning false if the username already exists.
elgg_ok_response($content= '', $message= '', $forward_url=null, $status_code=ELGG_HTTP_OK)
Prepares a successful response to be returned by a page or an action handler.