PHPMailer doesn't recognize to address

Question

I'm using phpmailer to send emails to addresses stored in the variable $to, but this

$mail->AddAddress($to);

results in this error message

You must provide at least one recipient email address.

I have tried printing $to and it prints out the correct email address where I want the message to be sent. The mail gets sent if I put in an email address instead of $to. Could anyone help? Thanks!

This is the code in question:

// if the email seller form is submitted
if ($_SERVER["REQUEST_METHOD"] == "POST")
{

// retreive the seller's email using his id
$seller_id = $_GET["sellerid"];

// query for the seller's email
$user_query = query("SELECT username FROM users WHERE id = ?", $seller_id);
$to = $user_query[0]["username"];   

// send an email to the seller
require_once("PHPMailer/class.phpmailer.php");

// instantiate mailer
$mail = new PHPMailer();

// use your ISP's SMTP server
$mail->IsSMTP();
$mail->Host = "smtp.fas.harvard.edu";

// set From:
$mail->SetFrom($_POST['buyer_email']);

// set To:
$mail->AddAddress($to);

// set Subject:
$mail->Subject = $_POST['subject'];

// set body
$mail->Body = $_POST['message'];

// set alternative body, in case user's mail client doesn't support HTML
$mail->AltBody = "Please view this message in an HTML-enabled browser.";

// send mail
if ($mail->Send() === false)
    die($mail->ErrorInfo . "\n");

This is the query function

    /**
* Executes SQL statement, possibly with parameters, returning
* an array of all rows in result set or false on (non-fatal) error.
*/
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, USERNAME, 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;
}

}

Answer 1

Ensure that $to has a valid email attached to it. From the looks of it is might have a username? $to = $user_query[0]["username"];