How can I implement this into a html page?

[jokke86]

There's a similar method for any type of input.
A textarea isn't like the other inputs because it's a different tag. Instead of a value input, the "value" is just placed between the tags. So modify the code above like this:
<textarea name="name"><?php if (!empty($_POST['name'])) { echo htmlentities($_POST['name']); } ?></textarea>

Note that this method works for most types of input, perhaps with some manipulation (such as for a checkbox).
However, for a select menu (maybe radio buttons as well) it becomes more complicated because you need to use a loop to determine which value was selected.

Very late reply (9 years later), but how can you implement this into a html page? The PHP processor is a seperate .php document.
Thanks!

[Winfrey]

Don't load view twice, try to remove the loading of view from if($this->form_validation->run()== FALSE) because when the view loads then set_value inside it is triggered and you have called loading view after creating captcha. So remove the load view when validation errors are there like,
....
if($this->form_validation->run()== FALSE) {
/*echo "valid";
print_r($this->input->post());
exit;*/
$data['mainpage']='index';
// comment the below line, otherwise there are no loophole in your code
//$this->load->view('templates/template',$data);
}
....