A PHP Error was encountered

Severity: Notice

Message: Only variable references should be returned by reference

Filename: core/Common.php

Line Number: 257

Fatal error: Uncaught Error: Call to undefined function mysql_pconnect() in E:\xampp\htdocs\upload\system\database\drivers\mysql\mysql_driver.php:91 Stack trace: #0 E:\xampp\htdocs\upload\system\database\DB_driver.php(115): CI_DB_mysql_driver->db_pconnect() #1 E:\xampp\htdocs\upload\system\database\DB.php(148): CI_DB_driver->initialize() #2 E:\xampp\htdocs\upload\system\core\Loader.php(346): DB(Array, NULL) #3 E:\xampp\htdocs\upload\system\core\Loader.php(1171): CI_Loader->database() #4 E:\xampp\htdocs\upload\system\core\Loader.php(152): CI_Loader->_ci_autoloader() #5 E:\xampp\htdocs\upload\system\core\Controller.php(51): CI_Loader->initialize() #6 E:\xampp\htdocs\upload\system\core\CodeIgniter.php(308): CI_Controller->__construct() #7 E:\xampp\htdocs\upload\index.php(202): require_once('E:\\xampp\\htdocs...') #8 {main} thrown in E:\xampp\htdocs\upload\system\database\drivers\mysql\mysql_driver.php on line 91