git clone --depth=1 https://github.com/nmathewson/Libevent.git
cd Libevent
./autogen.sh

./configure --prefix=/usr/local/libevent
make && make install

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

[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