Retrieve data from db and show in dynamic select

Capture the string from the foreach loop in a single variable and then return that, like this:

$options = ''; // String variable to return
$result = $wpdb->get_results("SELECT * FROM mytable WHERE id = $customer_id");
foreach ($result as $row) {
    $first_name = $row->firstName;
    $last_name = $row->lastName;
    $email .=  $row->email;
    $options .= '<option value="' . $email . '">' . $first_name . ' ' . $last_name . '</option>'; // Append option HTML to the $options variable
}
return $options; // Return $options after the loop

For security purposes, I’d also highly recommend using sanitizing and escaping functions. Alternatively, if you return a JSON encoded array, DTX can do that for you (see documentation).

Hello and thanks for you answer.

I have try your code, but it return and populate the select with only 1 result.
(If i try to echo instead return, the script give 2 result, so i am sure to have more then 1 result).

Thank you

Instead of using echo, can you use var_dump($row) inside the foreach loop to check how many times it’s looping? I sometimes wrap it in <pre> element tags to display it better like:

$options = ''; // String variable to return
$result = $wpdb->get_results("SELECT * FROM mytable WHERE id = $customer_id");
foreach ($result as $row) {
    echo '<pre>'; var_dump($row); echo '</pre>';
    $first_name = $row->firstName;
    $last_name = $row->lastName;
    $email .=  $row->email;
    $options .= '<option value="' . $email . '">' . $first_name . ' ' . $last_name . '</option>'; // Append option HTML to the $options variable
}
return $options; // Return $options after the loop

If it’s looping correctly, you should see both objects on the page and their values.

The only other thing I can think of is maybe the email address is empty for one of your entries?

And not that it really should make a difference, but I tend to write the values in SQL strings surrounded by double quotes, in case for some reason there’s spaces in whatever I’m using in the where clause, but again, this part is all preference and shouldn’t really affect how you’re making the request.

$where = sprintf('id="%s"', esc_attr($customer_id));
$sql = "SELECT * FROM mytable WHERE {$where}";
$rows = $wpdb->get_results($sql);
if(is_array($rows)) {
    foreach($rows as $row) {
        echo('<pre>'); var_dump($row); echo('</pre>');
    }
}

Hello, I’m marking this as resolved as I haven’t heard back from you in a while. If the issue still exists, please create a new one. Thanks!