Get 2nd Dropdown Value Based on First Dropdown Chosen

Question

JS

   <script type="text/javascript">
        $(document).ready(function(){
        $("#FirstDD").change(function(){
            $('#SecDD').load('inc/subcategories.php?scatID='+this.value);
            });
        });
        </script>

PHP

   <select style="width:300px;" id="FirstDD" name="userListingCategory">
                          <option  disabled="disabled">Category...</option>
                          <?php while($row = $sth2->fetch(PDO::FETCH_ASSOC))
                          {echo "<option value=". $categoryID . ">" .$row['catName']."</option>";}
                        unset($sth2);
                        ?>

                    </select> 
                   <select style="width:340px;" id="SecDD" name="userListingSCategory" style="display:none">
                    <?php require_once('inc/subcategories.php'); ?>
                    </div>
                    </select> 

subcategories.php

#GET SELECT category names
$pdo2 = new PDO($h1, $u, $p);
$pdo2->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
$sth2 = $pdo2->prepare("
SELECT catID, catName FROM Category
;");
$sth2->execute(array());

#GET SELECT sub-category names
$pdo3 = new PDO($h1, $u, $p);
$pdo3->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
$sth3 = $pdo3->prepare("
SELECT scatID, scatName 
FROM Category C, SubCategory SC
WHERE C.catID = SC.catID
AND SC.catID = '$categoryID'
;");
$sth3->execute(array());
?>

<option  disabled="disabled">Sub-Category...</option> 
<?php
#Get subcats     
while($row = $sth3->fetch(PDO::FETCH_ASSOC))
{echo "<option value=". $row['scatID'] . ">" .$row['scatName']."</option>";}
unset($sth3);
?>

Problem I'm having I select the first dropdown category , then the 2nd dropdown clears out but doesnt populate with the values of subcategories.php . I think this is because $sth2 is being unset() and trying to use $categoryID variable after that (in the $sth3 query ). How do I fix this??

Answer 1

Here are the issues that I imagine are keeping your code from working how you think it should:

In "PHP":

You need the $sth3 be set before attempting to use it.

I suggest moving the line

<?php require_once('inc/subcategories.php'); ?>

to somewhere above the line:

<?php while($row = $sth2->fetch(PDO::FETCH_ASSOC))

Next I think you need to change this line:

{echo "<option value=". $categoryID . ">" .$row['catName']."</option>";}

to

{echo "<option value=". $row['catID'] . ">" .$row['catName']."</option>";}

In subcategories.php:

I don't see where $categoryID is being set. So if it is not being set from the GET params then add:

if(!empty($_GET['scatID'])) $categoryID = (int)$_GET['scatID'];
else $categoryID = -1; // Something bogus

before

#GET SELECT category names
$pdo2 = new PDO($h1, $u, $p);