php - Symfony2 initialize error -

i have problem symfony2 project. on localhost works fine, on server got error:

"catchable fatal error: argument 1 passed symfony\component\httpfoundation\session\attribute\attributebag::initialize() must of type array, string given, called in /home/visset/ftp/cms/dashboard/app/cache/dev/classes.php on line 252 , defined"

i checked , initialize() function passed empty string.

what reason of problem?