Fatal error in Codeigniter

i have installed Codeigniter on xampp when i run codeigniter it gives me this error I am using Ubuntu 12.04
Warning: Unknown: failed to open stream: Permission denied in Unknown on line 0

Fatal error: Unknown: Failed opening required '/opt/lampp/htdocs/CodeIgniter-3.0.0/index.php' (include_path='.:/opt/lampp/lib/php') in Unknown on line 0

Seems like your Apache user (probably www-data) does not have read access to the index.php file. Try modifying the files to 644 and the folders to 755.