在PHP中，include和require的主要區(qū)別在於處理文件缺失的方式。使用include時，若文件不存在，會產(chǎn)生警告（E_WARNING），但腳本會繼續(xù)執(zhí)行；而使用require時，若文件不存在，會導致致命錯誤（E_COMPILE_ERROR），腳本立即停止。因此，1. 對於非關鍵文件如模板或可選組件，應使用include；2. 對於關鍵文件如配置文件或核心庫，必須使用require以避免後續(xù)錯誤。此外，為防止重複引入，還可使用include_once和require_once。常見錯誤是將require文件誤用為include，導致後續(xù)不可預見的問題。

The main difference between include and require in PHP comes down to how they handle errors when the file you're trying to load isn't found.

• If you use include and the file is missing, PHP will throw a warning ( E_WARNING ), but the script will continue to execute.
• If you use require , and the file is missing, PHP will throw a fatal error ( E_COMPILE_ERROR ), and the script will stop immediately.

So, require is stricter — it ensures that your script doesn't proceed without essential files. Use require for critical files (like configuration or core libraries), and include for optional ones (like templates or extra features).

When to Use include

Use include when the file you're loading isn't absolutely necessary for the script to run properly. For example:

• Loading a sidebar template
• Including optional widgets or banners
• Adding non-critical language files

If that file is missing, the site can still function — maybe with a placeholder or fallback content.

Example:

 include 'sidebar.php';

Even if sidebar.php is missing, the rest of the page will still load.

When to Use require

Use require when the file is crucial for your application to work. This includes:

• Configuration files (eg, database settings)
• Core classes or libraries
• Initialization scripts

If these files are missing, continuing execution would likely cause more errors, so PHP stops right away.

Example:

 require 'config.php';

If config.php is missing, PHP halts execution and displays a fatal error.

Practical Tips for Choosing Between Them

Here's a quick guide to help you decide which one to use:

• ? Use require for anything your app depends on to start or run.
• ? Use include for optional or visual components that don't break functionality.
• ? Remember: You can also use include_once and require_once if you want to avoid multiple inclusions.

A good rule of thumb:

If your app can't run without it — use require .
If it's just part of the layout or an extra feature — use include .

A Common Mistake to Avoid

Many developers accidentally use include for important files like autoloader scripts or config files — which can lead to confusing bugs later on.

For example:

 include 'database.php'; // Should be require

If this file fails to load, the script continues, and any further database calls will fail with undefined function/class errors. That makes debugging harder than it needs to be.

That's basically it. The distinction is simple but powerful once you understand how each affects script behavior.

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