character encoding of the HTML document was not declared codeigniter
When you refresh that page you get a blank one, if you view source that page you'll see it's blank that is has a number count. My guess is that you're doing something when the page refreshes that sends a white space to the browser. I can only suggest not to close your files with ?> and let php handle how your scripts will exit/die. There's some whitespace in your code that's causing that.
try adding these in head section of your view:
<meta content="text/html;charset=utf-8" http-equiv="Content-Type"><meta content="utf-8" http-equiv="encoding">
FOUND SOLUTION
In the first lines of Session class constructor, it loads the String helper.Yesterday I've created a helper called string_helper.php and this conflict was what crashing application.
I renamed my string_helper.php file and now everything works fine.
Thanks all!