安装mcrypt

先确认你的php和pecl版本

[root@lyafei ~]# php -v
PHP 7.2.26 (cli) (built: Dec 31 2019 17:01:19) ( NTS )
Copyright (c) 1997-2018 The PHP Group
Zend Engine v3.2.0, Copyright (c) 1998-2018 Zend Technologies
[root@lyafei ~]# pecl version
PEAR Version: 1.10.10
PHP Version: 7.2.26
Zend Engine Version: 3.2.0

确认你的linux有没有安装mcrypt库

[root@lyafei ~]# yum list installed | grep mcrypt
libmcrypt.x86_64                      2.5.8-13.el7                   @epel      
libmcrypt-devel.x86_64                2.5.8-13.el7                   @epel      
mcrypt.x86_64                         2.6.8-11.el7                   @epel      

以上显示已经安装过，若没有则按以下两种方式安装：

（方法一）yum命令安装

yum install libmcrypt libmcrypt-devel mcrypt mhash

确定安装，最后显示

Installed:
  libmcrypt.x86_64 0:2.5.8-13.el7.centos
  libmcrypt-devel.x86_64 0:2.5.8-13.el7.centos
  mcrypt.x86_64 0:2.6.8-11.el7
  mhash.x86_64 0:0.9.9-1.el7.rf

Complete!

（方法二）源码编译安装

去 http://www.sourceforge.net 下载 libmcrypt，mhash，mcrypt安装包

先安装libmcrypt

tar -zxvf libmcrypt-2.5.8.tar.gz
cd libmcrypt-2.5.8
./configure
make
make install

安装mhash

tar -zxvf mhash-0.9.9.9.tar.gz
cd mhash-0.9.9.9
./configure
make
make install

安装mcrypt

tar -zxvf mcrypt-2.6.8.tar.gz
cd mcrypt-2.6.8
LD_LIBRARY_PATH=/usr/local/lib ./configure
make
make install

安装php的mcrypt扩展(动态加载编译)

下载 php 的 mcrypt 扩展或者直接下载 php 的完整安装包
http://cn.php.net/releases/ 网页下找到自己服务器的 php 版本，下载后 tar 解压（本人的是 php 7.2.26）

wget  http://pecl.php.net/get/mcrypt-1.0.1.tgz
tar xf mcrypt-1.0.1.tgz
cd mcrypt-1.0.1

[root@lyafei mcrypt-1.0.1]# /usr/local/php/bin/phpize
Configuring for:
PHP Api Version:         20170718
Zend Module Api No:      20170718
Zend Extension Api No:   320170718
[root@lyafei mcrypt-1.0.1]# ./configure --with-php-config=/usr/local/php/bin/php-    config  && make && make install
checking for grep that handles long lines and -e... /usr/bin/grep
checking for egrep... /usr/bin/grep -E
checking for a sed that does not truncate output... /usr/bin/sed
......
Build complete.

在 php.ini 加上扩展即可

extension = mcrypt.so

重启 php-fpm

service php-fpm restart

这个时候查看 phpinfo 就可以看到 mcrypt 模块加载了