Simple PHP OOP -> Insert to database - php

Question

i am having some problem with my code, i try to simple insert some logs when user use search on my site.
Log should contains:
date in unix time -> using function for it
username -> its stored in Session
vin -> its string he post in input field
Top of the class
public $vin = null;
public function __construct( $data = array() )
{
if( isset( $data['vin'] ) )
$this->vin = stripslashes( strip_tags( $data['vin'] ) );
}
public function storeFormValues( $params )
{
$this->__construct( $params );
}
function code:
public function logFromSearch() {
$correct = false;
//$this->username = $_SESSION]['username'];
$date = new DateTime();
try {
$con = new PDO( DB_HOST, DB_USER, DB_PASS );
$con->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
$sql = "INSERT INTO logs(date, user, vin) VALUES(:date, :user, :vin)";
$stmt = $con->prepare( $sql );
$stmt->bindValue( "date", $date->getTimestamp(), PDO::PARAM_STR );
$stmt->bindValue( "user", $this->username, PDO::PARAM_STR );
$stmt->bindValue( "vin", $this->vin, PDO::PARAM_STR );
echo $this->vin;
echo $date->getTimestamp();
$stmt->execute();
return "Everything is OKEY";
} catch( PDOException $e ) {
return $e->getMessage();
}
}
Its not importing anything to database dispite the fact it should in my opinion. I try to debug it so i found out my way of adding username from session is not possible way and also find out that this->vin and $date->getTimestamp() is returning actual data which it should insert to database so can somebody help me to find where is the problem? (in same class i am using other function for database connection and they work find so its not in setting up connecting / db name and host and so on because its in different file)
P.S. Errors : I dont get any errors just single notice Notice: Undefined property: Data::$username which is understandable.