先下载libmemcached：
wget https://launchpad.net/libmemcached/1.0/1.0.18/+download/libmemcached-1.0.18.tar.gz
解包：tar -zxf libmemcached-1.0.18.tar.gz
进入解压后的包，编译安装：
./configure --prefix=/usr/local/libmemcached --with-memcached //注意：--with-memcached这个选项一定要加上
make && make install
安装完成后，开始安装memcached模块：
解包：tar zxvf memcached-2.2.0b1.tgz
进入解压后的包：cd memcached-2.2.0b1
phpize (或者/usr/local/php/bin/phpize)
./configure --with-php-config=/usr/local/php/bin/php-config --with-libmemcached-dir=/usr/local/libmemcached --disable-memcached-sasl
发现报错：
error: no, sasl.h is not available. Run configure with --disable-memcached-sasl to disable this check
解决方法：
当前目录下找到memcached.h
find / -name memcached.h
出现如下信息：
/home/local/libmemcached-1.0.18/libtest/memcached.h
/home/local/libmemcached-1.0.18/libmemcached-1.0/struct/memcached.h
/home/local/libmemcached-1.0.18/libmemcached-1.0/memcached.h
/home/local/libmemcached-1.0.18/libmemcached/memcached.h
/usr/local/libmemcached/include/libmemcached-1.0/memcached.h
/usr/local/libmemcached/include/libmemcached-1.0/struct/memcached.h
/usr/local/libmemcached/include/libmemcached/memcached.h
修改php_libmemcached_compat.h：
vim php_libmemcached_compat.h
找到include
改成
#ifndef PHP_LIBMEMCACHED_COMPAT
#define PHP_LIBMEMCACHED_COMPAT
/* this is the version(s) we support */
#include </usr/local/libmemcached/include/libmemcached/memcached.h>
将<>里面的内容替换成：/usr/local/libmemcached/include/libmemcached/memcached.h
然后
./configure --with-php-config=/usr/local/php/bin/php-config --with-libmemcached-dir=/usr/local/libmemcached --disable-memcached-sasl
make && make install
cp /usr/local/php/lib/php/extensions/no-debug-zts-20131226/memcached.so /usr/local/php/extension/memcached.so
vim /usr/local/php/etc/php.ini 添加： extension=memcached.so
/usr/local/apache/bin/apachectl restart
php -m
出现了memcached即安装成功