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