Php 在Mac上安装drush

我想在MAC上安装Drush，我遵循以下步骤：“只有在Drush目录中运行“composer install”时出错

我从DrushGitHub（）下载了Drush

该项目即将生成一个自定义Drush命令，以将旧Drupal项目设置（.yml文件）导出到新项目

错误在于没有设置版本？我发现这个：“我试图降级版本，但仍然是相同的错误

错误消息：

Loading composer repositories with package information
Installing dependencies (including require-dev) from lock file
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Installation request for drush/drush No version set (parsed as 1.0.0) -> satisfiable by drush/drush[No version set (parsed as 1.0.0)].
    - drupal/core 8.7.x-dev conflicts with drush/drush[No version set (parsed as 1.0.0)].
    - Installation request for drupal/core 8.7.x-dev -> satisfiable by drupal/core[8.7.x-dev].

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您是否尝试安装特定版本，如

composer global require drush/drush:9.*

？是的，出现了相同的错误您是否尝试安装特定版本，如

composer global require drush/drush:9.*

？是的，出现了相同的错误