php - Failing prepared statement. Not getting string -

i getting following error line of code...

warning: mysqli::query() expects parameter 1 string, object given 

for

        if ($result2 = $con->query($stmt2)) { 

and cannot figure out? connections correct, prepared statement above it. have tried moving stuff on page , read because mixing mysqli , mqsql, how doing sql?

what causing error?

try { $cid = $_get['cid']; $tid = $_get['tid']; $userid = ( isset( $_session['user'] ) ? $_session['user'] : "" );     echo $cid . "<br>";     echo $tid; //prepare if ($stmt = $con->prepare("select * forum_topics `category_id`=? , `id`=? limit 1")) {      $stmt->bind_param("ii", $cid, $tid);     $stmt->execute();     $stmt->bind_result($topic_id, $category_id, $topic_title, $topic_creator, $topic_last_user, $topic_date, $topic_reply_date, $topic_views);       //var_dump($stmt);      if (!$stmt) {         throw new exception($con->error);     } } $stmt->store_result(); $numrows = $stmt->num_rows; echo $numrows;   if($numrows == 1){     echo "<table width='100%'>";     if ( $_session['user'] ) {          echo "<tr><td colspan='2'><input type='submit' value='add reply' onclick=\"window.location =      'forum_post_reply.php?cid=".$cid."$tid=".$tid."'\"> <hr />";     } else {         echo "<tr><td colspan='2'><p>please log in add reply</p><hr /></td></tr>";     }     }      while ($row = $stmt->fetch()) {          //prepared select stmt forum posts         if($stmt2 = $con->prepare("select `id`, `category_id`, `topic_id`, `post_creator`, `post_content`, `post_date` forum_posts `category_id`=? , `topic_id`=?")) {          //var_dump($stmt2);              $stmt2->bind_param("ii", $cid, $tid);             $stmt2->execute();             $stmt2->store_result();             $stmt2->bind_result($post_id, $post_category_id, $post_topic_id, $post_creator, $post_content, $post_date);             if (!$stmt2) {             throw new exception($con->error);             }         }     }     if ($result2 = $con->query($stmt2)) {         while ($row2 = $result2->fetch_assoc() ) {             echo "<tr><td valign='top' style='border: 1px solid #000000;'>             <div style='min-height: 125px;'>".$row['topic_title']."<br />             ".$row2['post_creator']." - " .$row2['post_date']. "<hr />" . $row2['post_content'] ."</div></td>             <td width='200' valign='top' align='center' style='border: 1px solid #000000;'>user info here!</td></tr>             <tr><td colspan='2'><hr /></td></tr>";         }        }   else {         echo "<p>this topic not exist.</p>";         } } catch (exception $e) {     echo "error: " . $e->getmessage(); } 

it because trying execute query string using prepared statement object: in code $stmt2 prepared statement object $stmt2 = $con->prepare("selec