Upgrade Codeigniter 1.7.1 to 3.6

Indeed, as cartalot said, you don't need to upgrade through each version, one by one. Just read all the instructions to upgrade between your version and the target one, and build a list of things to do, then you can execute that list on one go. Here are some of the things that I added to my list when upgrading from 1.7.2 to 3.1.3.

• Add return parent::__get($prop); to your _get magic methods (if you have them).

• Replace $this->validation->error_string with validation_errors()

• Replace in views $this->validation->field_name with set_value(‘field_name’) and set_select(), etc.. And add the value to be used to pre-populate each field. But take in account that set_value() does not work if you don’t run form_validation->run() first.

• When retrieving data: Replace $this->validation->field_name and $this->form_validation->field_name with $this->input->post(‘field_name’)

• When setting data: Replace $this->form_validation->field_name with $this->form_validation->set_data($data);

• Take in account that set_data($other_data) overwrites the content of $_POST, so you need to merge $other_data and $_POST.

Good luck, and just power through it!.