仅当用户来自该页面时，如何在表单提交后将CodeIgniter中的URL重定向回上一页？

I've tried several ways to redirect the URL back to the page where the user came from after submitting a form or just refresh the form page to allow the user to make a new entry if the user came directly to it. So far, I've been unsuccessful. The following method is the closest I've got but I'm not sure what's going wrong -I've tried several ways to redirect the URL bac