注意：会话已经启动 - 忽略第2行的C：\ xampp \ htdocs \ teller \ fungsi.php中的session_start（）

i get a notice

Notice: A session had already been started - ignoring session_start() in C:\xampp\htdocs\teller\fungsi.php on line 2
Notice: Use of undefined constant status - assumed 'status' in C:\xampp\htdocs\teller\fungsi.php on line 17
Notice: Use of undefined constant status - assumed 'status' in C:\xampp\htdocs\teller\fungsi.php on line 20

in my code. I try this function in the old my sql version was success. but in my sql versi 5.5.16 it doesn't work. this is my source code :

<?php 
session_start();
function ver_user($username,$password)
{
    mysql_connect('localhost', 'root', '');
    mysql_select_db('teller');
    if (!empty($username)) 
        {
            $query="SELECT * FROM `user` WHERE `username`='$username'";
            $action=mysql_query($query);
            $data=mysql_fetch_array($action);
            $passmd5=md5($password);
            if ($data['password']==$passmd5)
                {
                    $_SESSION['username']=$username;
                    $_SESSION['password']=$password;
                    if ($data[status]==1){
                        $data['0']="valid";
                    }
                    if ($data[status]==2) {
                        $data['0']="valid1";
                    }   
                    return $data;
                }
            else 
                {
                    $data['0']="invalid";
                    return $data;
                }
        }
}
function logout()
{
    session_destroy();
}
?>

The second and third warning are because

$data[status]

should be

$data['status']

There isn't enough information in the question to explain why you get the warning about session_start(). You need to check more of the code to find where you're calling session_start() before this.