Codeigniter Search by category and or question title.

I am trying to be able to create a search model function all in one.

Where if user types in some thing like 

how to

It will search for that match title in questions

But the if the user would like to search for all questions in a category it will display all questions belong to that category.

I have this model function

PHP Code:

public function getQuestions($search = NULL) {
$this->db->select('*');
$this->db->from('questions');
$this->db->join('categories', 'categories.category_id = questions.question_id');
$this->db->join('questions_category', 'questions_category.category_id = categories.category_id');
$this->db->like('questions.title', $search, 'match');
$this->db->or_like('categories.name', $search, 'match');
$query = $this->db->get();

if ($query->num_rows() > 0) {
return $query->result_array();
} else {
return false;
}
} 


I have also tried using or_where

PHP Code:

public function getQuestions($search = NULL) {
 $this->db->select('*');
$this->db->from('questions_category');
$this->db->join('categories', 'categories.category_id = questions_category.question_id');
$this->db->join('questions', 'questions.question_id = questions_category.question_id');
$this->db->like('questions.title', $search, 'match');
$this->db->or_where('categories.name', $search);
$query = $this->db->get();

if ($query->num_rows() > 0) {
return $query->result_array();
} else {
return false;
}
} 


It seems to display it twice as shown in image and not correct questions 

Question: if use trys to search for a question it will try and find it in questions but if the user searches for a category it will display all questions belong to that category how can I make that work in one model function using join

Search url when searching for all questions in category

Code:

http://localhost/project-ask/questions/tagged/codeigniter

Search URL when searching for question

Code:

http://localhost/project-ask/questions/tagged/how-to

There's only one rule - please don't tell anyone to go and read the manual.  Sometimes the manual just SUCKS!

I think I may have it working now

PHP Code:

public function getQuestions($search = NULL) {
  $this->db->select('*');
  $this->db->from('questions q');
  $this->db->join('questions_category qc', 'qc.question_id = q.question_id', 'LEFT');
  $this->db->join('categories c', 'c.category_id = qc.category_id', 'LEFT');

  $this->db->or_like('q.title', $search, 'match');
  $this->db->or_where('c.name', $search);
  $query = $this->db->get();

  if ($query->num_rows() > 0) {
    return $query->result_array();
  } else {
    return false;
  }
} 


There's only one rule - please don't tell anyone to go and read the manual.  Sometimes the manual just SUCKS!