[php] Codeigniter's `where` and `or_where`

I'm trying to specify a query in my model

$this->db
        ->select('*')
        ->from('library')
        ->where('library.rating >=', $form['slider'])
        ->where('library.votes >=', '1000')
        ->where('library.language !=', 'German')
        ->where('library.available_until >=', date("Y-m-d H:i:s"))
        ->or_where('library.available_until =', "00-00-00 00:00:00")
        ->where('library.release_year >=', $year_start)
        ->where('library.release_year <=', $year_end)
        ->join('rating_repo', 'library.id = rating_repo.id')

So, the trouble i'm having is with my or_where. I want the or to be restricted to only the available_until field. Currently, however, i'm getting results which have a language of German which isn't what i want. How do i restrict my or_where filter to the available_until field only?

You can use : Query grouping allows you to create groups of WHERE clauses by enclosing them in parentheses. This will allow you to create queries with complex WHERE clauses. Nested groups are supported. Example:

$this->db->select('*')->from('my_table')
        ->group_start()
                ->where('a', 'a')
                ->or_group_start()
                        ->where('b', 'b')
                        ->where('c', 'c')
                ->group_end()
        ->group_end()
        ->where('d', 'd')
->get();

https://www.codeigniter.com/userguide3/database/query_builder.html#query-grouping

You can change your code to this:

$where_au = "(library.available_until >= '{date('Y-m-d H:i:s)}' OR library.available_until = '00-00-00 00:00:00')";
$this->db
    ->select('*')
    ->from('library')
    ->where('library.rating >=', $form['slider'])
    ->where('library.votes >=', '1000')
    ->where('library.language !=', 'German')
    ->where($where_au)
    ->where('library.release_year >=', $year_start)
    ->where('library.release_year <=', $year_end)
    ->join('rating_repo', 'library.id = rating_repo.id');

Tip: to watch the generated query you can use

echo $this->db->last_query(); die();

$this->db->where('(a = 1 or a = 2)');

You may group your library.available_until wheres area by grouping method of Codeigniter for without disable escaping where clauses.

$this->db
    ->select('*')
    ->from('library')
    ->where('library.rating >=', $form['slider'])
    ->where('library.votes >=', '1000')
    ->where('library.language !=', 'German')
    ->group_start() //this will start grouping
    ->where('library.available_until >=', date("Y-m-d H:i:s"))
    ->or_where('library.available_until =', "00-00-00 00:00:00")
    ->group_end() //this will end grouping
    ->where('library.release_year >=', $year_start)
    ->where('library.release_year <=', $year_end)
    ->join('rating_repo', 'library.id = rating_repo.id')

Reference: https://www.codeigniter.com/userguide3/database/query_builder.html#query-grouping