因为要编译php的memcached扩展，所以需要这个库。为了省事，我使用的是brew自动安装

brew install libmemcached

安装到一半，提示错误

checking for libevent directory... configure: error: libevent is required.  You can get it from http://www.monkey.org/~provos/libevent/

      If it's already installed, specify its path using --with-libevent=/dir/

但是libevent是安装过的，使用命令

brew install libevent

显示

Warning: It appears you have Macports or Fink installed
Software installed with other package managers causes known problems for
Homebrew. If formula fail to build uninstall Macports/Fink and reinstall any
affected formula.
Warning: Formula already installed: libevent

这又是怎么回事呢？难道非要我去下载源代码编译吗？