即使我更改参数，也会得到相同的查询结果

I have a query that I am using to get results that are newer than a given timestamp. It is supposed to find all those newer messages that were sent and received by a given user. The problem is, no matter what I change the timestamp parameter to, I even changed it to 'g', I still get 4 results. The timestamp doesn't seem to alter my query. In the table, the timestamp is an int(11). I tried using intval and defining the bindvalue as a param int and still no luck. Any ideas?

$sql = 'SELECT timestamp, user, message, receiver, convo_id
          FROM chatbox 
         WHERE user = ? 
            OR receiver = ? 
           AND timestamp = ? 
      ORDER BY timestamp DESC';

$stmt = $conn->prepare($sql);
$stmt->bindValue(1,'username');
$stmt->bindValue(2,'username');
$stmt->bindValue(3,'g');
$stmt->execute();

I suspect it's the precedence of AND and OR in your where clause. Try using parentheses:

WHERE ( user = ? OR receiver = ?  )
  AND timestamp = ?

assuming that's what you need.

Shouldn't you do this instead in your $sql variable?

AND timestamp > ?