访问一个域时如何避免共享会话

Question

用户同时登录网站后，我遇到了有关共享会话的问题。当最后一个用户登录时，每个用户都会查看最后一个用户的帐户，这是不合适的（我猜安全问题）。所有用户必须登录同一网站，并且必须仅为特定用户显示输出。

我正在使用PHP代码。有没有人也经历过这些情景？这是代码

function validate_login(){
    $userName= trim((isset($_POST['username']) === TRUE ? $_POST['username'] : ''));
    $userPass= trim((isset($_POST['userpass']) === TRUE ? $_POST['userpass'] : ''));
    $userNameArray  = explode("@", $userName);
    $userName       = $userNameArray[0];
    $compLogin      = ((isset($userNameArray[1]) === TRUE ? $userNameArray[1]: ''));

    $KeepAlive = new KeepAlive();
    if(isset($userNameArray[1])){
    if(!$this->Login->checkattempt('admin')){
    $loginArray = array(
    'login' => $userName,
    'comp_login_string' => $compLogin,
    'pass' => $cryptography->encryptPassword($userPass)
    );

    $userCredentials = $this->Login->getLogin($loginArray);
    if(!empty($userCredentials)){
    $_SESSION['userCredentials'] = $userCredentials[0];
    header('Content-Type: application/json');
    $_SESSION['employee_user']  = '0';
    $_SESSION['emp_id']         = '0';
    $_SESSION['page']['client_ip_address']  = $KeepAlive->get_client_ip();
    $_SESSION['page']['last_trans_time']        = time();
    $this->Login->clear_attempt_log($_POST, 'admin');
    echo json_encode(array('id' => $userCredentials[0]['id']));
    }
    } else {
    array_shift($loginArray);
    $this->Login->attempt_log($_POST, 'admin');
    header('Content-Type: application/json');
    echo json_encode(array('id' => '-1'));
    }
    } else {
    echo json_encode(array('id' => '-2'));
    }
}