将php变量添加到下拉菜单中（在Flask中）

I originally had this script to populate a dropdown menu with query results:

<?php
require_once("dbcontroller.php");
$db_handle = new DBController();
if(!empty($_POST["data_id"])) {
    $query ="SHOW COLUMNS FROM table_name";
    $results = $db_handle->runQuery($query);
?>
    <option value="">Select Parameter</option>
<?php
    foreach($results as $col) {
?>
    <option value=""><?= $col ?></option>
<?php
    }
}

However the entry was always empty. I checked if this was a php syntax problem using both <?= and <?php echo as suggested in Populating dropdown list

No luck. So next I checked if there actually is something in my query result so I simple replaced the dropdown entry with a string variable:

<?php
$varName= 'testingList';
?>
    <option value=""><?= $varName ?></option>

Again I tried both syntax options but still no luck (i.e. testingList does not show up in the dropdown). Instead, I get a new blank dropdown option i.e. 1 empty entry is added. (PS. the value assigned will also be the same variable but I'm leaving it out at the moment to make sure its not an issue - so just focusing on getting a variable name in the dropdown menu).

Currently running PHP 5.5.9 on a remote server; the issue is also local. Any ideas greatly appreciated. Thanks!

UPDATE

When I run the .php file independently, works just fine. But not in the flask environment so I thought I'll add the fact that I'm working in Flask.

I have fixed this by switching everything to flask. Since this was a multiple dropdown menu, i.e. the value selected in the first dropdown populates the second dropdown, I sent the selected value from the first dropdown back to flask through Ajax, and populated the second dropdown using flask!

You need to echo the Field from $col, Try this:

<option value=""><?= $col['Field'] ?></option>