private function bind($stmt) {

		$meta 	= $stmt -> result_metadata();
		$double = [];
		$vars 	= [];

		if($stmt -> field_count > 0) {

			while($field = $meta -> fetch_field()) {

				$columnname  = $field -> name;
				${$columnname} = null;
				
				if(true === array_key_exists($columnname, $vars)) {
					$double[] = $columnname;
				}
				else {
					$vars[$columnname] = &${$columnname};
				}
			}
		}

		if(count($double) > 0) {
			return trigger_error(sprintf('Column %s in field list is ambiguous', implode(', ', array_unique($double))));
		}

		call_user_func_array([$stmt, 'bind_result'], $vars);

		return $vars;
	}