PHP中$_REQUEST无法获取Cookie及登录跳转后失效问题求助

Hey there! Let's break down why you're having trouble accessing cookies via $_REQUEST after logging in and redirecting to show_user.php—I'll walk through the most common causes and fixes:

1. PHP config is excluding cookies from $_REQUEST #

By default, $_REQUEST combines data from $_GET, $_POST, and $_COOKIE—but this behavior depends on two php.ini settings:

• request_order: Determines the merge order. If it's set to GP (only GET/POST) instead of GPC, cookies won't show up in $_REQUEST.
• variables_order: Another related setting that needs to include C (for cookies) to populate the global cookie pool.

Fixes:

• Check your php.ini and set these to include C, e.g., request_order = "GPC" or variables_order = "EGPCS".
• If you can't edit php.ini, skip $_REQUEST entirely and use $_COOKIE directly—it's more reliable for cookie-specific data and avoids config-dependent behavior.

2. Your cookie was set with incorrect parameters #

If the cookie's path, domain, or security settings are off, it won't be sent to show_user.php:

• Path mismatch: If you set the cookie with path="/signin" during login, it will only be accessible under the /signin directory. Set path="/" instead to make it available across your entire site.
• Domain issues: If your login page is on a subdomain (e.g., auth.yoursite.com) and show_user.php is on the main domain, you need to set domain=".yoursite.com" to let the cookie cross subdomains.
• Secure/Httponly notes: httponly blocks JavaScript from reading cookies but doesn't affect PHP's $_COOKIE. If your site uses HTTPS, ensure secure=true so browsers only send the cookie over encrypted connections.

Example of a properly set cookie:

// Login success: set a cookie valid for 24h, accessible site-wide
setcookie("user_session", $session_id, time() + 86400, "/", "", false, false);

3. You didn't terminate the script after redirecting #

When you call header("Location: show_user.php") right after setting a cookie, you must add exit() or die() immediately after. Without this, PHP might continue executing code, which can corrupt the response headers and prevent the cookie from being saved by the browser.

Wrong way:

setcookie("user_id", $user_id);
header("Location: show_user.php");
// Script keeps running—response headers might break

Right way:

setcookie("user_id", $user_id, time() + 86400, "/");
header("Location: show_user.php");
exit(); // Critical: stops script execution to ensure headers are sent correctly

4. Name conflicts between cookies and GET/POST data #

If your cookie shares a name with a GET or POST parameter (e.g., both named user_id), $_REQUEST will prioritize the value from $_GET or $_POST (depending on request_order), overwriting the cookie value. Using $_COOKIE['your_cookie_name'] avoids this ambiguity entirely.

1. After setting the cookie in signin.php, immediately print var_dump($_COOKIE) to confirm the cookie was set correctly.
2. In show_user.php, print both var_dump($_COOKIE) and var_dump($_REQUEST) to compare—if the cookie exists in $_COOKIE but not $_REQUEST, it's a config issue.
3. Check your browser's dev tools (Application > Cookies) to verify the cookie is stored, and that its path/domain matches the URL of show_user.php.

内容的提问来源于stack exchange，提问作者Shanojan.A