$result_array[] += $c;
$new_item = $new_item + $c;
//преобразуется в
//$new_item = NULL + object
//арифметическое сложение преобразует в
//$new_item = 0 + 1
//итог
//$new_item = 1;
$result_array[] = $new_item;
$result_array[] = $c;
$sql_query = 'SELECT COUNT(*) FROM content WHERE user_id = :user_id';
$sql_param = array('user_id'=>$_SESSION['user_id']);
$result = $this->db->prepare($sql_query)->execute($sql_param)->fetchcolumn();