Composer php composer dump autoload-命令

我不理解

composer dump autoload

命令的描述：

If you need to update the autoloader because of new classes in a classmap package for example, you can use "dump-autoload" to do that without having to go through an install or update.
Additionally, it can dump an optimized autoloader that converts PSR-0/4 packages into classmap ones for performance reasons. In large applications with many classes, the autoloader can take up a substantial portion of every request's time. Using classmaps for everything is less convenient in development, but using this option you can still use PSR-0/4 for convenience and classmaps for performance. 

为什么它会说

dump。。。出于性能原因

？为什么要卸载优化的装载机？ 是“出于性能原因而转储”还是“出于性能原因而转换”

如果它是“性能转储”，那么为什么它会说“性能类映射”

如果是“性能转换”，为什么要卸载自动加载器

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我很困惑。

它转储自动加载程序使用的类映射。这样，自动加载程序就不需要搜索文件系统来找到正确的文件，它已经知道该文件了。这将节省时间。

类映射并非在所有情况下都更快。在将其用于生产之前，请小心并衡量您从中获得的好处

有关详细信息，请参见我的回答：