php - Installing opencart on localhost -

i took complete backup of opencart web server database.now want install on localhost can make changes @ code, , can test locally.so copied folder root directory of local server.the made new database it.then edit config.php file looks this.

    <?php // http define('http_server', 'http://localhost/sillypunter/ocart/'); define('http_catalog', 'http://localhost/sillypunter/ocart/') // https define('https_server', 'http://localhost/sillypunter/ocart/');  // dir define('dir_application', 'sillypunter/ocart/catalog/'); define('dir_system',     'sillypunter/ocart/system/'); define('dir_database',  'sillypunter/ocart/system/database/'); define('dir_language', 'sillypunter/ocart/catalog/language/'); define('dir_template', 'sillypunter/ocart/catalog/view/theme/'); define('dir_config',  'sillypunter/ocart/system/config/'); define('dir_image', 'sillypunter/ocart/image/'); define('dir_cache', 'sillypunter/ocart/system/cache/'); define('dir_download', 'sillypunter/ocart/download/'); define('dir_logs', 'sillypunter/ocart/system/logs/');  // db define('db_driver', 'mysqli'); define('db_hostname', 'localhost'); define('db_username', 'sp_user'); define('db_password', 'sp1234'); define('db_database', 'sp_ocar'); define('db_prefix', 'sp_'); ?> 

but on browser giving me server error 500.i'am using ubuntu 14.04,apache2, mysql , php. please me solve problem.

define('dir_application', $_server['document_root'].'sillypunter/ocart/catalog/'); define('dir_system', $_server['document_root'].'sillypunter/ocart/system/'); define('dir_database', $_server['document_root'].'sillypunter/ocart/system/database/'); define('dir_language', $_server['document_root'].'sillypunter/ocart/catalog/language/'); define('dir_template', $_server['document_root'].'sillypunter/ocart/catalog/view/theme/'); define('dir_config', $_server['document_root'].'sillypunter/ocart/system/config/'); define('dir_image', $_server['document_root'].'sillypunter/ocart/image/'); define('dir_cache', $_server['document_root'].'sillypunter/ocart/system/cache/'); define('dir_download', $_server['document_root'].'sillypunter/ocart/download/'); define('dir_logs', $_server['document_root'].'sillypunter/ocart/system/logs/');