Could you explain, perhaps, why you want to do this? If you're trying to get the title of the page in javascript, you can do so easily using document.title
. If you want to have a unique ID value, you can either put it in a hidden input box with the id "page_value" or something like that, or you can simply put it in a global javascript variable. If you'd like to pass the id value of the page to the next page in a POST request without using flashdata, you can put it in a hidden input box with name "page_value" or something. If you want to temporarily store data for the next page load in CodeIgniter, you can use CI's flashdata in the sessions class:
http://codeigniter.com/user_guide/libraries/sessions.html
But, if you do want to give the body a unique id depending on what page it's on (and even though I think this approach is a bit misguided), you will have to look at your template system's insertion methods. You could probably make a secondary title in your template class that takes the title value and strips out whitespace characters and replaces it with dashes. Something like this:
function stringURLSafe($string)
{
//remove any ' ' from the string and replace with '-'
$str = str_replace(' ', '-', $string);
// lowercase and trim
$str = trim(strtolower($str));
return $str;
}