PHP - 未定义的会话

Question

I'm attempting to make a login system, which then redirects to the appropriate pages if the right details were entered or not.

session_start();

$result = mysqli_query($con, "my query");
if(mysqli_num_rows($result) == 1)
{
    $_SESSION['username'] = $username;
    header("Location: home.php");
}
else
{
    header("Location: login.php");
}

However, if I enter the right details I get: "Undefined variable: _SESSION".

I don't really know what's going wrong here.

Answer 1

You need to make sure that you start session ( session_start()) at the top of every php file where you want to use the $_SESSION superglobal array.