错误使用CodeIgniter form_validation（）函数抛出致命错误

I'm trying to apply CodeIgniter's form validation feature for an input form in one of my view pages. In that form, all fields are required. If all the fields are successfully filled up and then if the user clicks the submit button, it will redirect to another view page with the list of entries. If any field is left empty, validation messages will be displayed. I'm trying to apply CodeIgniter's form validati