You can achieve this through Codeigniter's autoload configuration.
Edit your project's autoload.php which is located in directory YourProject/application/config/
$autoload['libraries'] = array('REST_Controller');
And in controllers access this library class through $this->rest_controller.
BTW: Rest_Controllers is a library file, so I don't think a name suffixed with Controller is a good name for it.
Edit
Through your comment I got that you actually mean all of your controllers extended from REST_Controller, and you don't want require it at the top of every controller file.
Solution:
- Move
REST_Controller.php into directory YourProject/application/core/.
- In
YourProject/application/config/config.php line 119 change $config['subclass_prefix'] = 'MY_'; to $config['subclass_prefix'] = 'REST_';
then Codeigniter will load REST_Controller automatically.
But the subclass_prefix config has a global effect, and you need change the location of REST_Conttoller.php, so to make minimal change I think the best way is you create MY_Controller class in directory ./application/core/ and require REST_Controller at bottom of this new file. When CI load MY_controller automatically REST_Controller will be required too.
Notice: MY_Controller need extending from CI_Controller