PHP会话有时无法重启

Question

I have a PHP script which returns a receipt to a customer purchasing on my website. When they get the receipt, I want to be able to start a new session. So far I have a piece of code at the end of the script which returns the receipt page. It is:

if (ini_get("session.use_cookies")) {
    $params = session_get_cookie_params();
    setcookie(session_name(),
    '',
    time() - 42000,
    $params["path"],
    $params["domain"],
    $params["secure"],
    $params["httponly"]
    );
}

session_destroy();
session_regenerate_id(true);

When I use the website and go through the purchasing process, after the receipt page is served, the session id remains the same.

Yet, I took the above code and placed it in a seperate script called 'regenerate.php'. I then called this in another script, like so:

<?php
    include("regenerate.php");
    session_start();
    echo("<br>id:".session_id());

    include("regenerate.php");
    session_start();
    echo("<br>id:".session_id());

    include("regenerate.php");
    session_start();
    echo("<br>id:".session_id());

    include("regenerate.php");
    session_start();
    echo("<br>id:".session_id());
?>

When I run this script, then session id changes each time the regenerate script is run. However, the same code does not work in the intended page I am trying to serve up before restarting the session.

Is there any reason it might work in one case and not the other? I thought it might be because text is already being written out to output, however it happens in both cases.

Answer 1

You can't generate a new session during the same request, after sending output to the browser.

Simply because the session cookie has already been sent - with the headers. So most likely your second call to session_start() gives an error.

You can find more about turning display_errors On here: How do I get PHP Errors to display?