I need to filter per country first through dropdown select by country, then autosuggest/autocomplete on  the input textbox the companies under the countries selected. 

My question is  : How do I pass the variable from dropdown? 
Here are by codes below :

1st page (index)

1. //dropdown 
2.   <select name="f_country_id" class="form-control" id="f_country_id">
3.    <option value="?cid=0&code=0" >-- Select Country --</option>
4. <?php
5. while($country = $sql_getCountries->fetch_assoc()){
6. echo '<option ';
7. if($country['id'] == $_GET['cid']){
8. echo ' selected ';
9. }
10. echo 'value="?cid='.$country['id']'.'">'.$country['d_name'].'</option>';
11. }
12. ?>
13.   </select> 
14. 
    
15. <input type='text' name='d_name' value='' class='auto form-control' id="d_name"  placeholder="Name of Company/Establishment" >
16. 
    
17. <!--- start here Autoload ////////// --->
18. <script type="text/javascript" src="http://code.jquery.com/jquery-1.9.1.min.js"></script>
19. <script type="text/javascript" src="http://code.jquery.com/ui/1.10.1/jquery-ui.min.js"></script>
20. <script type="text/javascript">
21. $(function() {
22. 
    
23. //autocomplete
24. $(".auto").autocomplete({
25. source: "auto_search.php" ,
26. //minLength: 1
27. });
28. 
    
29. });
30. </script>
31. <!--- End here Autoload Scripts ////////// --->

2nd page (auto_search.php)

2. if (isset($_GET['term'])){
3. $return_arr = array();
4. 
   
5. try {
6.     $conn = new PDO("mysql:host=".DB_SERVER.";dbname=".DB_NAME, DB_USER, DB_PASSWORD);
7.     $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
8. 
   
9. $stmt = $conn->prepare("SELECT a.* FROM tb_company_establishment a  WHERE a.d_name LIKE :term");
10.     $stmt->execute(array('term' => '%'.$_GET['term'].'%'));
11.     
12.     while($row = $stmt->fetch()) {
13.         $return_arr[] =  $row['d_name'];
14.     }
15. 
    
16. } catch(PDOException $e) {
17.     echo 'ERROR: ' . $e->getMessage();
18. }
19. 
    
20. 
    
21.     /* Toss back results as json encoded array. */
22.     echo json_encode($return_arr);
23. }

If only i can pass from the dropdown country variable to auto_search page then it can solve the problem.

Hope you can help me, im not used to jquery or javascript.

Thanks in advance