Custom session save_handler overwerites current saved data in database - php

Question

So I finally managed to save some session data in to the database.
Now a new problem arises. When I load the page once all data is being saved.
When I reload the page and I write something to the session all data that's already in the session is being replaced with this new data. This means that with each load all the data is being replaced for new data. This is giving me problems because I'm saving a order_id into the session when there is no order_id present in the session.
This is the code that writes the data into the database. And yes it says replace into. But because this is a custom handler how can i actually append data to this current session with out renewing everything. Also how can I replace old data for new data witch is already present in the session.
The code that handles the writing to the database.
function _write($id, $data) {
$access = time();
$id = $this->session_db->real_escape_string($id);
$access = $this->session_db->real_escape_string($access);
$data = $this->session_db->real_escape_string($data);
$sql = "REPLACE INTO sessions VALUES ('$id', '$access', '$data')";
return $this->session_db->query($sql);
}
Is there something that i can do to put all the data directly after session_start() in the session variable so it always has all the data and doesn't overwrite the data with a single value when I do something like:
$_SESSION['LAST_ACTIVITY'] = time(); ?
EDIT: Also when I try to echo the session directly after the session_start();
It gives me there error
Warning: session_start(): Failed to decode session object. Session has been destroyed in /var/www/vhosts/url/httpdocs/index.php on line 13
Is there something wrong with the serialized string I don't understand why it is giving me this error.
Thanks in advance, some help will be appreciated.

Answer 1

Ok so now everything is working. I kinda feel embarrassed for saying what the problem was. So ok the problem and the solution.
The problem was that the session serialized data was way to long for a regular text field in the database. My string was over 500.000 characters long regular text field in database supports until 65.000+ characters.
So I changed the field from "TEXT" to "LONGTEXT" now it has enough space to save the string. And now everything works properly.
Everybody thanks for your time so far.