codice:
function DBFieldMustBeNotNull($dbname, $tablename, $fieldname)
{
    $resource = mysql_list_fields($dbname, $tablename);
    $columns = mysql_num_fields($resource);

    for ($i = 0; $i < $columns; $i++)
        {
        if ($fieldname == mysql_field_name($resource, $i))
            {
            $flags = mysql_field_flags ($resource, $i);
            break;
            }
        }

    $flag_array = explode(" ", $flags);

    if (in_array("not_null", $flag_array))
        return true;
    else
        return false;