Create a file called form_validation_lang.php as shown below
- application / language / english / form_validation_lang.php
Go to system / language / english / form_validation_lang.php find.
$lang['form_validation_is_unique'] = 'The {field} field must contain a unique value.';
Copy the key above, then add to the application / language / english / form_validation_lang.php
$lang['form_validation_is_unique'] = 'The {field} entered is already in use.';
Further
About Add Controller Form Validation
$this->lang->load('form_validation', 'english');
how
$this->lang->load('form_validation', 'english'); $this->form_validation->set_rules('username', 'Username', 'trim|required|is_unique[users.username]');
Note. If you use form_validation is_unique in other controllers and want to use this message, you will need to load this $this->lang->load('form_validation', 'english'); On to this controller if you do not decide to autoload it.
Mr. ED source share