PHP重定向不工作通常由以下原因?qū)е拢?. 頭部已發(fā)送，如空格、HTML或include文件輸出；2. header()使用錯(cuò)誤，如語法問題或缺少exit；3. 邏輯未觸發(fā)，如條件判斷錯(cuò)誤；4. 緩存或服務(wù)器行為乾擾。解決方法包括避免提前輸出、正確使用header()並加exit、檢查邏輯流程、清除緩存或使用工具檢測(cè)響應(yīng)。

If your PHP redirect isn't working, you're probably running into one of a few common issues. The most likely culprits are headers already being sent, incorrect syntax, or output before the header() call. Let's go over some specific scenarios and what to check.

1. Headers Already Sent

One of the most frequent problems with redirects in PHP is that something has already been output before the header() function runs — even a single space or newline will break it.

• This includes:
  • Extra spaces before <?php or after ?>
  • Echo statements or HTML before the header
  • Included files that have trailing spaces or output

What to do:

• Make sure there's no output before header('Location: ...')
• Avoid closing ?> at the end of PHP-only files
• Use output buffering if needed ( ob_start() at the top)

You'll often see an error like this:

 Warning: Cannot modify header information - headers already sent by...

2. Incorrect Usage of header()

Even if you're using the right function, small mistakes can cause it not to work as expected.

Common issues include:

• Missing quotes or parentheses in the header() call
• Using relative URLs without proper context
• Forgetting to exit after sending the header

Example of correct usage:

 header("Location: https://example.com");
exit;

Tips:

• Always use quotes around the string (single or double)
• Use full URLs when possible to avoid confusion
• Add exit or die() after the redirect to stop further execution

3. Redirect Logic Not Triggering

Sometimes the code is fine, but the redirect never gets reached because of how the logic flows.

This usually happens when:

• The redirect is inside a conditional block that doesn't evaluate to true
• There's a typo in the condition or path
• You're testing locally and forgot the redirect was only for certain cases

What to do:

• Double-check your conditions ( if , switch , etc.)
• Add temporary debugging output like echo "Redirect should happen"; before the header
• Make sure the script reaches the header() line by checking logs or adding breakpoints

4. Caching or Browser Behavior

In some cases, the redirect works, but it seems like it doesn't due to browser caching or server-level redirects interfering.

Things to try:

• Clear your browser cache or test in incognito mode
• Use tools like Postman or curl to inspect actual HTTP responses
• Check .htaccess or web server config for conflicting rules

So, start by checking for early output, then confirm your syntax and logic flow. If everything looks good but still not working, look into caching or server-level settings.基本上就這些.

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