Libevent 是一个用C语言编写的、轻量级的开源高性能I/O框架，支持多种 I/O 多路复用技术： epoll、 poll、 dev/poll、 select 和 kqueue 等；支持 I/O，定时器和信号等事件；注册事件优先级。PHP提供了对应的扩展 libevent、 Event 。
相比 libevent ext, event ext 拥有更好的性能表现和更全面的API，可以让我们更友好的使用 Libevent。
安装 Libevent 库
php event 扩展 依赖 Libevent 库，需要先编译安装（注意是 Libevent 库，非 libevent 扩展）。
git clone --depth=1 https://github.com/nmathewson/Libevent.git cd Libevent ./autogen.sh ./configure --prefix=/usr/local/libevent make && make install
安装 Event 扩展
可以直接使用 pecl 安装
pecl install event downloading event-2.5.3.tgz ... Starting to download event-2.5.3.tgz (140,913 bytes) ..............................done: 140,913 bytes 50 source files, building running: phpize Configuring for: PHP Api Version: 20180731 Zend Module Api No: 20180731 Zend Extension Api No: 320180731 Enable internal debugging in Event [no] : Enable sockets support in Event [yes] : libevent installation prefix [/usr] : /usr/local/libevent ... Build process completed successfully Installing '/usr/local/php/lib/php/extensions/no-debug-non-zts-20180731/event.so' install ok: channel://pecl.php.net/event-2.5.3 Extension event enabled in php.ini
查看安装结果
[root@localhost ~]# php --ri event event Event support => enabled Sockets support => enabled Debug support => disabled Extra functionality support including HTTP, DNS, and RPC => enabled OpenSSL support => enabled Thread safety support => disabled Extension version => 2.5.3 libevent2 headers version => 2.2.0-alpha-dev
