I have big problem related to login. actually some time it work fine but some time not working. I have setting.php in which session_start() is executing. this file is including in all file. another file is config.php where all variable is defined including session name

$siteConfig_session_name =  dhoombox ;

然后创建了一个类用户，其中有如下函数userlogin：-

function user_front_end_login($_POST,$checkout_page,$check){
    $errorMessage =   ;
    $userName = trim($_POST[ username ]);
    $password = md5(trim($_POST[ password ]));
$user_login = mysql_query("SELECT user_id, email_id,username, password , firstname, lastname, status FROM tbl_users WHERE  username=  ".$userName."  AND password =  ".$password."  ");
    $select_user = mysql_fetch_array($user_login);
if( mysql_num_rows($user_login)==1){
    $user_status = $select_user[ status ];
    //setAdminError( <span class="errormsg">Information has not been deleted!</span> );
        if( $user_status==1){

                 $this->setUserLoginSession($select_user[ user_id ], $select_user[ email_id ], $select_user[ username ],$select_user[ firstname ],$select_user[ lastname ]);


                    if($checkout_page==1){
                    siteRedirect("billing_info.php");
                    }
                    else{

                     print_r($_SESSION);
                     siteRedirect("index.php");
                    }

            }else{
                setAdminError( <span class="errormsg" style="color:#FF0000;">Sorry your account is not activated.</span> );     siteRedirect("login.php");
            }
    }else{
               setAdminError( <span class="errormsg" style="color:#FF0000;">Username or password mismatch</span> );
                    if($checkout_page==1){
                    siteRedirect("checkout.php");
                    }
                    else{                   
                    siteRedirect("login.php");
                    }       
            }
} 

$this->；setUserLoginSession（$select_user[user_id]、$select_user[email_id]、$select_user[用户名]、$sectit_user[名字]、$Sectit_user[姓氏]）；如下所示：-

function setUserLoginSession($uid, $email, $un, $fn,$ln) {
    global $siteConfig_session_name;

     $_SESSION[ user_id ]   = $uid;
     $_SESSION[ email_id ]  = $email;
     $_SESSION[ username ]  = $un;
     $_SESSION[ firstname ] = $fn;
     $_SESSION[ lastname ]  = $ln;
}

有时它工作良好，有时则不然。