聽說 memcached 安裝之後，網站會變得飛快，所以就試著安裝了看看。參考文章如下：
http://www.ipserverone.info/control-panel/how-to-install-memcached-and-l...
https://www.howtoforge.com/how-to-use-multiple-php-versions-php-fpm-and-...
http://stackoverflow.com/questions/22102326/install-pecl-memcached-error
http://stackoverflow.com/questions/24407095/error-when-installing-pecl-m...
http://stackoverflow.com/questions/11274078/unable-installing-php-extens...
http://stackoverflow.com/questions/683864/can-i-install-the-memcached-ph...
http://m.wangchao.net.cn/it/tcdetail_66092.html
https://www.digitalocean.com/community/tutorials/how-to-install-and-use-...
PECL 的 memchace 套件
http://pecl.php.net/package/memcached