Problem with database query

There's a fundamental flaw in your join statements.
Join will ask you for the field in table 1 that corresponds with the field in table 2.
If you just want to join records that have the value "accept" in the field votes.content, simply use a where statement.
E.g.:

PHP Code:

$this->db
->select('p.content, p.id, p.userid, v.userid, v.content')
->from('posts p')
->join('users u','p.userid = u.id')
->join('votes v','v.postid = p.id')
->where('v.questionid', $debate['id'])
->where('v.content','accept')
->where('p.floor',0);
$query = $this->db->get();
echo $this->db->last_query();
$records = $query->result_array();