Session problem

Hello everyone;
help me ;
Since i am going to version 3.1.3 of codeigniter. I a problem that keeps me from putting my site online.
In local everything works well;
But as soon as I put the site online I errors regarding the sessions.


Here is an apperception of the error:
   

The file controllers/Login.php generates output where it should not.
In your local environment you probably have a different error reporting level so it is not shown to you, but the same error exists

Possibly you use a closing ?> tag at the end of your controller and have an empty line below it.