centos 5
rpm -ivh http://mirrors.ustc.edu.cn/fedora/epel//5Server/x86_64/epel-release-5-4.noarch.rpm
centos 6
rpm -ivh http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-5.noarch.rpm
更新后 yum search php53-mcrypt 或者 yum search mcrypt
看到更新后的列表中已经出现了 php53-mcrypt
安装 yum install php53-mcrypt
安装成功后,重启web service 即可