1.
#首先需要安装libmemcached库
yum -y install libmemcached libmemcached-devel

2.
#下载memcached扩展
wget https://github.com/php-memcached-dev/php-memcached/archive/php7.zip
#解压
unzip php7.zip

3.
cd php-memcached-php7/
/usr/local/php/bin/phpize
#配置
./configure --with-php-config=/usr/local/php/bin/php-config

4.
make
make install
安装后会出现Installing shared extensions: *****PHP的扩展目录，此目录一般为默认的php扩展目录

5.
在php.ini中添加memcached扩展

extension=memcached.so
重启php-fpm使之生效:service php-fpm restart

6.
启动memcached:
/usr/bin/memcached -d -l 127.0.0.1 -p 11211 -m 150 -u root

7.
应用:
$mem = new Memcached;//初始化
$mem->addServer("127.0.0.1", 11211);//连接
$mem->add('shw4', 'hello tes4324234t!',60);//添加
$mem->replace('shw4', 'hello tes4324234t!',60);//替换
$mem->set('shw4', 'hello tes4324234t!',60);//如果不存在就新增，存在就替换,add和replace的结合
$mem->flush();//清除所有缓存
$val = $mem->get('shw4');//获取
 $val = $mem->delete('shw4');//删除