I thought double underscore always meant private function but what does it mean in cakephp 2.0 in such examples as this
http://book.cakephp.org/2.0/en/tutorials-and-examples/blog-auth-example/auth.html
For example
$this->Session->setFlash(__('The user could not be saved. Please, try again.'));
The double underscore function in CakePHP handles localization. It’s used when you want to translate your application by providing a string translation dictionary.
Cake PHP Book: Global Constants & Functions
See also Internationalization and Localization