php扩展memcached的作用是为了支持数据库缓存服务器，首先需要先编译安装好php，php具体安装步骤可参考本站（请在右上角搜索即可），安装好php之后，就可以用phpize安装memcached扩展。

下载libmemcached

https://launchpad.net/libmemcached/+download

# cd /usr/local/src
# wget https://launchpad.net/libmemcached/1.0/1.0.18/+download/libmemcached-1.0.18.tar.gz

安装libmemcached

# tar zxf libmemcached-1.0.18.tar.gz
# cd libmemcached-1.0.18
# ./configure --prefix=/usr/local/libmemcached --with-memcached
# make
# make install

下载memcached扩展

http://pecl.php.net/package/memcached

# cd /usr/local/src
# wget http://pecl.php.net/get/memcached-2.2.0.tgz

安装memcached扩展

# /usr/local/php/bin/phpize
# tar zxvf memcached-2.2.0.tgz
# cd memcached-2.2.0
# ./configure --enable-memcached --with-php-config=/usr/local/php/bin/php-config --with-libmemcached-dir=/usr/local/libmemcached --disable-memcached-sasl
# make
# make install

安装完成后，会在php的模块目录下生产memcached.so模块文件

修改php.ini，假如如下内容

[memcached]
extension=memcached.so

然后重启apache或者php-fpm，查看phpinfo页面是否加载成功，通过以下方法测试php客户端memcache连接memcached服务器端是否正常

在apache网站根目录下建立memcache.php文件

# vim memcache.php

添加如下内容：

 $memcache->set('key', 'Memcache test successful!', 0, 60);
 $result = $memcache->get('key');
 unset($memcache);
 echo $result;
 ?>