PHP登录会话和回显用户名

Question

The problem is on my login page everything works just fine but the problem here is when i successfully login the username doest show up at the main page.

include ('connect.php');

if (($_SERVER['REQUEST_METHOD'] == 'POST') && (!empty($_POST['action']))):
    $usernameLog = $_POST['usernameLog'];
    $passwordLog = $_POST['passwordLog'];
    $valid = true;

     if($valid == TRUE){
    include('connect.php');

    $usernameLog = mysql_real_escape_string($usernameLog);
    $passwordLog = mysql_real_escape_string(md5($passwordLog));

    $sql = mysql_query("SELECT * FROM register WHERE username = '$usernameLog' AND passconf = '$passwordLog'");


    if(mysql_num_rows($sql) > 0){

        //if true then lets go to the logged in page
        session_start();

        $_SESSION['logat'] = "da";

        header('location: BlogWorld.php');

I am not sure what's going wrong. Please help

//codes sesssion for the main page ie when user is successfully logged in

include('connect.php');

// Start session
    session_start();


// Check if user is logged and existing session
    if(isset($_SESSION['username'])) {
            include ("connect.php");

// Content for user logged
    echo "Welcome ".$username." :) - <a href='logout_Blog.php'>Logout</a>";
    } else {
// Redirecting to login page
    Header("Location: ./");

Answer 1

Add session_start() at the top of the pages where you are using session.

And store

$_SESSION['username'] = $usernameLog;

Then echo $_SESSION['username'];