[PHP知识库]Warning from https: |repo.packagist.org: Support for Composer 1 is deprecate

composer下载提示：

Warning from https://mirrors.aliyun.com/composer: You are using an outdated version of Composer. Composer 2.0 is now available and you should upgrade. See https://getcomposer.org/2

提示原因：您的composer版本太低（我的之前的版本是composer1.8.5），现在有了composer2的版本，那就要升级了。

解决办法：升级本地的composer版本
输入下面的命令：

composer self-update

这样就升级到了2.1.8版本。