protected function _create_placeholders($fields)
{
if (!empty($fields)) {
$db_fields = array();
foreach ($fields as $key => $value) {
// Process expression fields directly into the query
if (array_key_exists($key, $this->_expr_fields)) {
$db_fields[] = $value;
} else {
$db_fields[] = '?';
}
}
return implode(', ', $db_fields);
}
}