Ubuntu 20.04下PHP 8.1无法加载OpenSSL扩展导致Contao网站异常的求助

大家好，我最近把本地运行的Contao网站从Contao 3.5.40 + PHP 5.6升级到了Contao 4.13 + PHP 8.1，服务器环境是Ubuntu 20.04 + Apache2。网站大部分内容能正常显示，但遇到了两个问题：部分头部图片缺失，还有搜索栏功能完全损坏。

我查看了Apache2的错误日志，发现了几个关键报错信息：

[Fri Jan 05 11:57:04.458185 2024] [mpm_prefork:notice] [pid 128763] AH00169: caught SIGTERM, shutting down

PHP Warning:  PHP Startup: Unable to load dynamic library 'openssl' (tried: /usr/lib/php/20210902/openssl (/usr/lib/php/20210902/openssl: cannot open shared object file: No such file or directory), /usr/lib/php/20210902/openssl.so (/usr/lib/php/20210902/openssl.so: cannot open shared object file: No such file or directory)) in Unknown on line 0

PHP Warning:  Module "intl" is already loaded in Unknown on line 0

[Fri Jan 05 11:57:04.563161 2024] [mpm_prefork:notice] [pid 128837] AH00163: Apache/2.4.41 (Ubuntu) configured -- resuming normal operations

[Fri Jan 05 11:57:04.563230 2024] [core:notice] [pid 128837] AH00094: Command line: '/usr/sbin/apache2'

我去检查了PHP扩展目录/usr/lib/php/20210902/，确实找不到openssl相关的文件。

我尝试了以下几种解决方法，但都没成功：

• 首先尝试通过apt安装扩展：

  sudo apt-get install php8.1-openssl
  

  但返回错误：

  Reading package lists... Done
  Building dependency tree
  Reading state information... Done
  E: Unable to locate package php8.1-openssl
  E: Couldn't find any package by glob 'php8.1-openssl'
  E: Couldn't find any package by regex 'php8.1-openssl'
  

• 确认php.ini文件里的extension=openssl已经取消注释；
• 尝试用PHP源码编译安装：

  ./configure --with-openssl
  make
  sudo make install
  

现在实在没头绪了，有没有大佬能指点下，怎么解决OpenSSL扩展加载的问题？或者我的网站异常是不是还有其他隐藏原因？

备注：内容来源于stack exchange，提问作者Mesarich