Codeigniter displays a blank page instead of error messages

Since none of the solutions seem to be working for you so far, try this one:

ini_set('display_errors', 1);

http://www.php.net/manual/en/errorfunc.configuration.php#ini.display-errors

This explicitly tells PHP to display the errors. Some environments can have this disabled by default.

This is what my environment settings look like in index.php:

/*
 *---------------------------------------------------------------
 * APPLICATION ENVIRONMENT
 *---------------------------------------------------------------
 */
define('ENVIRONMENT', 'development');
/*
 *---------------------------------------------------------------
 * ERROR REPORTING
 *---------------------------------------------------------------
 */
if (defined('ENVIRONMENT'))
{
    switch (ENVIRONMENT)
    {
        case 'development':
            // Report all errors
            error_reporting(E_ALL);

            // Display errors in output
            ini_set('display_errors', 1);
        break;

        case 'testing':
        case 'production':
            // Report all errors except E_NOTICE
            // This is the default value set in php.ini
            error_reporting(E_ALL ^ E_NOTICE);

            // Don't display errors (they can still be logged)
            ini_set('display_errors', 0);
        break;

        default:
            exit('The application environment is not set correctly.');
    }
}

Make sure php5-mysql is installed.