Joomla error displaying the error page: Application Instantiation error: Failed to start the session

I am trying to run my Joomla website on localhost but getting following error:

Warning: session_start(): Failed to read session data: user (path: C:\xampp\tmp) in C:\xampp\htdocs\Joomla_3\libraries\joomla\session\handler\native.php on line 258
Error displaying the error page: Application Instantiation Error: Failed to start the session

I have tried to find the solution over Internet and made some changes on "configuration.php" file but still same error is coming again and again:
here is my config. file:

<?php class JConfig { public $MetaAuthor = '1'; public $MetaDesc = ''; public $MetaKeys = ''; public $MetaRights = ''; public $MetaTitle = '1'; public $MetaVersion = '0'; public $access = '1'; public $cache_handler = 'file'; public $cachetime = '15'; public $caching = '0'; public $captcha = '0'; public $cookie_domain = ''; public $cookie_path = ''; public $db = 'websitedb'; public $dbprefix = 'entdc1_'; public $dbtype = 'mysqli'; public $debug = '0'; public $debug_lang = '0'; public $display_offline_message = '1'; public $editor = 'tinymce'; public $error_reporting = 'default'; public $feed_email = 'none'; public $feed_limit = '10'; public $force_ssl = '0'; public $fromname = 'Wireless-site'; public $ftp_enable = '1'; public $ftp_host = ''; public $ftp_pass = ''; public $ftp_port = '21'; public $ftp_root = ''; public $ftp_user = ''; public $gzip = '1'; public $helpurl = 'https://help.joomla.org/proxy/index.php?option=com_help&keyref=Help{major}{minor}:{keyref}'; public $host = 'localhost'; public $lifetime = '15'; public $list_limit = '20'; public $live_site = ''; public $log_path = '/xampp/htdocs/Joomla_3/log'; public $mailer = 'mail'; public $mailfrom = ''; public $memcache_compress = '0'; public $memcache_persist = '1'; public $memcache_server_host = 'localhost'; public $memcache_server_port = '11211'; public $offline = '0'; public $offline_image = ''; public $offline_message = 'This site is down for maintenance.<br />Please check back again soon.'; public $offset = 'UTC'; public $offset_user = 'UTC'; public $password = 'admin'; public $robots = ''; public $secret = 'HHuagoT8gBoxPG7oyUoXmBD6hnq9oU2P'; public $sef = '1'; public $sef_rewrite = '1'; public $sef_suffix = '0'; public $sendmail = '/usr/sbin/sendmail'; public $session_handler = 'database'; public $sitename = 'Wireless-site'; public $sitename_pagetitles = '0'; public $smtpauth = '0'; public $smtphost = 'localhost'; public $smtppass = 'Nirvana001'; public $smtpport = '25'; public $smtpsecure = 'none'; public $smtpuser = 'dsrivastava'; public $tmp_path = '/xampp/htdocs/Joomla_3/tmp'; public $unicodeslugs = '1'; public $user = 'admin'; public $mailonline = '1'; public $cache_platformprefix = '0'; public $memcached_persist = '1'; public $memcached_compress = '0'; public $memcached_server_host = 'localhost'; public $memcached_server_port = '11211'; public $redis_persist = '1'; public $redis_server_host = 'localhost'; public $redis_server_port = '6379'; public $redis_server_auth = ''; public $redis_server_db = '0'; public $proxy_enable = '0'; public $proxy_host = ''; public $proxy_port = ''; public $proxy_user = ''; public $proxy_pass = ''; public $massmailoff = '0'; public $session_memcache_server_host = 'localhost'; public $session_memcache_server_port = '11211'; public $session_memcached_server_host = 'localhost'; public $session_memcached_server_port = '11211'; public $frontediting = '1'; public $asset_id = '1'; }

here is the index.php file:

<?php define('JOOMLA_MINIMUM_PHP', '5.3.10'); if (version_compare(PHP_VERSION, JOOMLA_MINIMUM_PHP, '<')) { die('Your host needs to use PHP ' . JOOMLA_MINIMUM_PHP . ' or higher to run this version of Joomla!'); } // Saves the start time and memory usage. $startTime = microtime(1); $startMem = memory_get_usage(); /** * Constant that is checked in included files to prevent direct access. * define() is used in the installation folder rather than "const" to not error for PHP 5.2 and lower */ define('_JEXEC', 1); if (file_exists(__DIR__ . '/defines.php')) { include_once __DIR__ . '/defines.php'; } if (!defined('_JDEFINES')) { define('JPATH_BASE', __DIR__); require_once JPATH_BASE . '/includes/defines.php'; } require_once JPATH_BASE . '/includes/framework.php'; // Set profiler start time and memory usage and mark afterLoad in the profiler. JDEBUG ? $_PROFILER->setStart($startTime, $startMem)->mark('afterLoad') : null; // Instantiate the application. $app = JFactory::getApplication('site'); // Execute the application. $app->execute();

I want to know the reason why my website is not running on localhost?
thanks for help.