check exist value coincidence

[eluser]Gabi3xz[/eluser]
I have a code for check exist a category in datebase

Code:

$result_cat = $this->call_db->category_check($this->input->post('cat_name'));
if ( $result_cat != false ) {
        echo 'Category not exist';
}

Works good but example
I go to a page for edit category, value category should always be another value because their finds value in the database and forced me to change the value category.
Iow do I solve?