How can I update record in database for a specific tab of page loading?

[colap]

How can I update record in database for a specific tab of page loading?

It's addform.php. there is a form to upload image through ajax into tmp_images table. this table has id,user_id,imagepath,post_id. post_id is irrelevant here. Everytime it inserts data with post_id=-1.

What I tried at top of addform.php:

    $user_id = $_SESSION['id'];
    $dbh = getDbconn();
    $stmt=$dbh->prepare("update tmp_images set mark=0 where user_id=:user_id and post_id=-1");
    $stmt->bindParam(':user_id',$user_id);
    $stmt->execute();

this updates all records for that user when the page loads/reloads/refreshes, problem is: if there are multiple 'addform.php' openned and multiple images have been uploaded by same user in different tabs, then if I refresh one tab it updates all records uploaded in different tabs too.

[requinix]

Sounds like post_id needs to be relevant.