Function set_value() not working as expected

[eluser]GreGre[/eluser]
You are using $this out of the object context.
Helpers are not classes, they are plain functions. If you want to use the codeigniter object inside a function you should instantiate it (inside each function) like this

Code:

$CI = & get_instance();

An than use $CI instead of $this

Code:

if ( ! isset($CI->_field_data[$field]))