Notice: Undefined index: user_id in E:\xampp\htdocs\public\series.php on line 5

Fatal error: Uncaught Error: Call to undefined function mysql_real_escape_string() in E:\xampp\htdocs\public\class.php:295 Stack trace: #0 E:\xampp\htdocs\public\series.php(5): Myclass->getSubjectUniversityInstructor(NULL) #1 {main} thrown in E:\xampp\htdocs\public\class.php on line 295