php SESSION var getting lost on my server.

 
    <?php
    //Start session
    session_start();
   
    //Include database connection details
    require_once('../Connections/golf_stats.php');
   
    //Array to store validation errors
    $errmsg_arr = array();
   
    //Validation error flag
    $errflag = false;
   
    //Connect to mysql server
    $link = mysql_connect($hostname_golf, $username_golf_stats, $password_golf_stats);
    if(!$link) {
        die('Failed to connect to server: ' . mysql_error());
    }
   
    //Select database
    $db = mysql_select_db($database_golf_stats, $golf_stats);
    if(!$db) {
        die("Unable to select database");
    }
   
    //Function to sanitize values received from the form. Prevents SQL injection
    function clean($str) {
        $str = @trim($str);
        if(get_magic_quotes_gpc()) {
            $str = stripslashes($str);
        }
        return mysql_real_escape_string($str);
    }
   
    //Sanitize the POST values
       
    $login = clean($_POST['login']);
    $password = clean($_POST['password']); 
   
    //Input Validations
    if($login == '') {
        $errmsg_arr[] = 'Login ID missing';
        $errflag = true;
    }
    if($password == '') {
        $errmsg_arr[] = 'Password missing';
        $errflag = true;
    }
   
    //If there are input validations, redirect back to the login form
    if($errflag) {
        $_SESSION['ERRMSG_ARR'] = $errmsg_arr;
        session_write_close();
        header("location: login.php");
        exit();
    }
   
    //Create query     
    mysql_select_db($database_golf_stats, $golf_stats);
    $query_members = "SELECT * FROM members WHERE username = '$login'";
    $list_members = mysql_query($query_members, $golf_stats) or die(mysql_error());
    $row_members = mysql_fetch_assoc($list_members);
    $totalRows_members = mysql_num_rows($list_members); 
       
    //Check whether the query was successful or not
    if($list_members) {
        if($totalRows_members == 1) {
            //Login Successful         
            $_SESSION['SESS_MEMBER_USERNAME'] = $row_members['username'];
            $_SESSION['SESS_JOUEUR_ID'] = $row_members['idJoueur'];
            $_SESSION['SESS_JOUEUR_NAME'] = $row_members['name'];
           
            session_write_close();
            header("location: ../members/members-index.php");
            exit();
        }else {
            //Login failed
            header("location: login-failed.php");
            exit();
        }
    }else {
        die("Queryisfailed");
    }
?>