PHP veritabanına veri kaydedilmiyor

$host = 'localhost';
$username = 'karbay_users';
$password = ')H1w[AdP-2XNYr_D';
$database = 'karbay_users';

try {
    $con = new PDO("mysql:host=$host;dbname=$database;charset=utf8", $username, $password);
    $con->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    if ($con->connect_error) {
        die("Bağlantı hatası meydana geldi: $con->connect_error");
    }
} catch (PDOException $e) {
    echo "Bağlantı hatası meydana geldi: ".$e->getMessage();
    exit();
}

Warning: Undefined property: PDO::$connect_error in D:\xampp\htdocs\assets\baglan.php on line 12

<?php
$host = 'localhost';
$username = 'karbay_users';
$password = parola
$database = 'karbay_users';
try {
    
    $con = new PDO("mysql:host=$host;dbname=$database;charset=utf8", $username, $password);
    $con->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch (PDOException $e) {
    echo "Bağlantı hatası meydana geldi: ".$e->getMessage();
    exit();
}
?>

<?php

// Veritabanı bağlanma
include_once '../includes/baglan.php';
session_start();

$username = $con->real_escape_string($_POST['username']);
$password = $con->real_escape_string($_POST['password']);

$sql = "SELECT * FROM users WHERE username = ?";
$stmt = $con->prepare($sql) or die ($con->error);
$stmt->bind_param('s',$username);
$stmt->execute();
$result_username = $stmt->get_result();
$row = $result_username->fetch_assoc();
$count_username = $result_username->num_rows;


if($count_username > 0 ) {
    
    $uid = $row['uid'];
    $username = $row['username'];
    $password_db = $row['password'];
    
    if(password_verify($password, $password_db)) {
        
        $_SESSION['uid'] = $uid;
        $_SESSION['username'] = $username;
        exit('success');

    } else {
            exit('errorPassword');
    }
    

} else {
    exit('errorUsername');
}

?>