每次页面刷新时，我的会话都取消设置

>我正在尝试使网站在那里，当管理员成功登录时，我有管理员登录系统，而不是分配会话，但此会话在页面刷新时过期。检查下面，我向您展示了我所做的事情。

目录

      <form  action="../../system/access/checking.php" class="form-signin">
    <h2 class="form-signin-heading">Please sign in</h2>
    <input type="text" id="user" class="form-control" placeholder="Email address"  required autofocus>
    <input type="password" id="pass" class="form-control" placeholder="Password"  required>
    <a class="btn btn-lg btn-primary btn-block"  onclick="submitfom();" >Sign in</a>

  </form>

阿贾克斯

function submitfom() {
$.ajax({
         type: "POST",
         url: "../../system/access/checking.php",
         data: {user: $("#user").val(),pass: $("#pass").val()},
         success: function(data){
      if(data == true ){     
      window.location.href = '../../index.php';
        } else {
          $('#show-error').slideDown( "slow",function (){$('#show- error').html(data);$('#show-error').css("display","inline");});
        };
     }
      });
  }

.php

 include('../../../config.php');
 if((isset($_POST['user'])) && (isset($_POST['pass'])) ){
 $user = $_POST['user'];
  $pass = $_POST['pass'];
       $query = mysql_query("SELECT user FROM admin_user WHERE user ='".$user."' ");
       $query2 = mysql_query("SELECT pass FROM admin_user WHERE pass ='".$pass."' ");
       $result= mysql_num_rows($query);
       $result2= mysql_num_rows($query2);
        if((!empty($result)) && (!empty($result2))){
          session_set_cookie_params('3600');
           session_start();  
            $_SESSION['admin']=$user ;
            session_write_close();
            echo true;
         }
      else {
           echo "Please Write correct <strong>username and password</strong>";
          }
                }
      else {
                 echo "Some thing miss";
           }