Php 会话在本地主机上工作，但有时在服务器上不工作

这是我正在创建会话的控制器：

public function login(){
    if(isset($_POST)){
        $res = $this->register_model->loginUser();
        if($res['result'] === true){
            // declare session variables
            $user = $res['info']; // array containing user information
            // set session variables
            $_SESSION['storeId'] = $user->str_id;
            $_SESSION['sName'] = $user->str_nme;
            $_SESSION['sId'] = $user->str_identifier;
            $_SESSION['hash'] = $user->hash;
            $res['info'] = null;
        }
    } else {
        $res = array('result'=>false,'msg'=>'Login failed. Please try again');
    }
    echo json_encode($res);
}

这是一个控制器，我在其中检索会话

public function login(){
    if(isset($_POST)){
        $res = $this->register_model->loginUser();
        if($res['result'] === true){
            // declare session variables
            $user = $res['info']; // array containing user information
            // set session variables

            $this->load->library('session');
            $newdata = array(
                'storeId'  => $user->str_id,
                'sName'     => $user->str_nme,
                'sId' => $user->str_identifier,
                'hash' => $user->hash,
                'info' => null,
                'logged_in' => TRUE,
            );

            $this->session->set_userdata($newdata);

        }
    } else {
        $res = array('result'=>false,'msg'=>'Login failed. Please try again');
    }
    echo json_encode($res);
}

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您得到的错误是什么？为什么将php会话代码与CI会话混合？请提供并阅读此内容