一、下载扩展包及依赖
libmemcached下载地址
https://launchpad.net/libmemcached/+download
php-memcached下载地址 （PHP5.6选择2.2.0版本，PHP7选择3.X版本）
http://pecl.php.net/package/memcached
二、安装libmemcached依赖
mkdir -p /usr/local/libmemcached
tar zxvf libmemcached-1.0.18.tar.gz
cd libmemcached-1.0.18
./configure --prefix=/usr/local/libmemcached --with-memcached
make && make install