debugging cs50 finance query function (php)

Question

I got this piece of piece code from csfinance from a few years ago. I was wondering how I can printf the error code on the very last else when the query gets returned as false? (for example if its a duplicate entry print duplicate entry). Thanks for your help in advance!

function query(/* $sql [, ... ] */)
{
    // SQL statement
    $sql = func_get_arg(0);

    // parameters, if any
    $parameters = array_slice(func_get_args(), 1);

    // try to connect to database
    static $handle;
    if (!isset($handle))
    {
        try
        {
            // connect to database
            $handle = new PDO("mysql:dbname=" . DATABASE . ";host=" . SERVER . ';charset=utf8mb4', USER, PASSWORD);

            // ensure that PDO::prepare returns false when passed invalid SQL
            $handle->setAttribute(PDO::ATTR_EMULATE_PREPARES, false); 
        }
        catch (Exception $e)
        {
            // trigger (big, orange) error
            trigger_error($e->getMessage(), E_USER_ERROR);
            exit;
        }
    }
    // prepare SQL statement
    $statement = $handle->prepare($sql);
    if ($statement === false)
    {
        // trigger (big, orange) error
        trigger_error($handle->errorInfo()[2], E_USER_ERROR);
        exit;
    }

    // execute SQL statement
    $results = $statement->execute($parameters);

    // return result set's rows, if any
    if ($results !== false)
    {
        return $statement->fetchAll(PDO::FETCH_ASSOC);
    }
    else
    {
        return false;
    }
}