composer.json中的require-dev部分是什麼？

require-dev在composer.json中用於列出僅在開發環境中需要的PHP包，如測試框架、代碼質量工具和調試器，這些不在生產環境中安裝。 1. 常見類型包括PHPUnit、PHPStan、Xdebug等。 2. 默認情況下composer install會安裝require和require-dev包，但生產環境應使用--no-dev標誌跳過dev依賴。 3. 使用composer require --dev可將包添加到require-dev。 4. 僅在開發或測試中需要的包應放在此處，而生產所需功能的包應放在require中。 5. 保持require-dev簡潔，不活躍使用的工具應刪除，CI/CD通常會安裝dev依賴。

If you've ever looked at a composer.json file and wondered what the require-dev section is for, you're not alone. In short, it's where you list PHP packages that are only needed in development environments — not in production.

This means tools like testing frameworks, code sniffers, debuggers, or anything else you use while building or maintaining the project doesn't get installed when the app goes live.

What kind of packages go in require-dev?

The main idea behind require-dev is to separate development-specific dependencies from those required for the application to run in production.

Here are some common types of packages you'll find in this section:

• Testing tools : PHPUnit, Pest, Codeception
• Code quality tools : PHPStan, Psalm, PHP_CodeSniffer
• Debugging tools : Xdebug, Laravel Debugbar (in some cases)
• Development helpers : PHP CS Fixer, Rector, Faker (sometimes)

These tools help developers write better code, test functionality, and catch issues early — but they don't need to be present once the app is deployed.

How does require-dev affect Composer commands?

When you run composer install , by default, Composer installs both require and require-dev packages — unless you tell it otherwise.

In production, you usually want to skip installing dev dependencies. To do that, you add the --no-dev flag:

 composer install --no-dev

This makes your production environment lighter and more secure by not including unnecessary packages.

Also, when you add a package using composer require , it goes into require by default. If you want it in require-dev , you need to specify it:

 composer require --dev phpunit/phpunit

When should you use require-dev?

You should use require-dev whenever a package isn't needed outside of development or testing.

For example:

• You're writing unit tests with PHPUnit → definitely a dev dependency.
• You're using Laravel Dusk for browser testing → dev only.
• You have a package that generates documentation → dev use only.

However, if a package adds functionality that's needed in production — like a library that handles payments or sends emails — it belongs in the regular require block.

One thing to note: if you're building a package or framework meant to be used by others, avoid putting optional tools in require . Instead, suggest them via "suggest" or put them in require-dev .

A few small but important details

• The order of packages in require-dev doesn't matter — Composer doesn't care about sorting.
• It's good practice to keep require-dev clean. If a tool isn't actively used, remove it.
• CI/CD pipelines often install dev dependencies because they run tests and linters.

Also, if you're sharing your package with others, remember: people consuming your package won't get your require-dev dependencies automatically — which is correct behavior.

So that's basically it. require-dev is just a way to keep your development tools organized and out of production. Not complicated, but easy to misuse if you're not paying attention.

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