PHP 安装 安装过程出现如下提示:PHP Startup: Unable to load dynamic library '/usr/local/php5.3/lib/php/extensions/no-debug-non-zts-20090626/memcached.so' - /usr/local/php5.3/lib/php/extensions/no-debug-non-zts-20090626/memcached.so: cannot open shared object file: No such file or directory in Unknown on line 0 请问这是什么原因?应该如何解决?