php connection to mysql db fails after ajax call - php

Question

I have a function that connects to Mysql DB that works great in a "normal" call, but fails to connect in response to ajax call.
The php code:
// return data to ShowDdl()
function getDDLdata($tablename) {
global $db;
$data = '';
$name = ($tablename == 'sapak' || $tablename == 'cupon' ? 'Name' : 'Hebrewname');
////****** $db IS NOT RECOGNIZED WHEN CALLING ShowDdl() FROM AJAX
////****** BUT WORKS GREAT IN NORMAL CALLS
$query = $db->select("SELECT `id` , `".$name."` AS name FROM `".$tablename."` ORDER BY `id` ASC");
for($i=0;$result = $db->get_row($query, 'MYSQL_ASSOC');$i++){
$data[$i] = $result;
}
return $data; // id, name
}
// echo ddl with current data from requested table
function ShowDdl($tablename, $sapakid = null) {
$possibletables = array (
'category', 'subcategory', 'brand', 'sapak', 'cupon'
);
$ddlname = '';
// find the correct name for the ddl
for ($i = 0; $i<count($possibletables); $i++) {
if ($possibletables[$i] == $tablename) {
// only cupon ddl should have different id and name
if ($tablename == 'cupon') {
$ddlname = 'sapak-'.$sapakid .'-cupon';
}
else {
$ddlname = 'product-' . $tablename;
}
continue;
}
}
echo '<select multiple id="'.$ddlname.'" name="'.$ddlname.'[]">';
$data = getDDLdata($tablename);
foreach ($data as $vn ) {
if ($vn['id'] != null) {
echo '
<option value="'.$vn['id'].'"> '.$vn['name'].' </option>
';
}
}
echo '</select>';
}
It works great when called from 'normal' php.
The ajax call:
$.ajax({
type: "GET",
url: 'moudels/product/generic_offer.php',
data: 'sid=' + sid + '&name=' + name,
success: function (data) {
$('<div id='+ sid + '> </div>').appendTo('#genericofferdiv');
// append the response to the new div
$("#"+sid).html(data);
}
});
I get this error:
Fatal error: Call to a member function select() on a non-object
I'm sure it it because the ajax call, maybe it can't load the global $db var correctly. Any ideas how I solve this?
Thank you very much
*Note: I know that I should use mysqli, but the whole project is build with this and I can't change it

Answer 1

When you call / include this file from within your php project, you probably defined somewhere the global variable $db and can access it in this file, too.
But if you call this from you website, all the php has run through and no global variable exist anymore...
-> So you have to include f.e. the config.php where you defined your $db variable again!
config.php:
$db = new mysqli(DB_HOST, DB_USER, DB_PW, DB_DB);
yourFile.php
require_once('./config.php');