某些ajax调用请求后会话未更新

I am updating a session using an ajax call.

PHP

public function mymethod() 
{
    //Session Increament
    $addrowcount=1;
    $addrowcount +=$this->session->userdata('row');
    $this->session->set_userdata('row', $addrowcount);
    echo $addrowcount;
}

jQuery

jQuery.ajax({url: "myurl.com/mycontroller/mymethod/",dataType: "json", async: false, success: function(data){}});

But the session is not updating or not getting increased after 20 to 23 ajax calls.

First check whether session library loading in controller or not and then try below PHP code.

public function mymethod() 
{ 
  //Session Increament
  $addrowcount=1;
  $addrowcount +=$this->session->userdata('row');
  $session_data=array('row' => $addrowcount);
  $this->session->set_userdata($session_data);
  echo json_encode($session_data);
}