Which operation system and version do you use?
Perhaps Ubuntu 20.04 LTS or Debian Bullseye?
I think there is no package “php-smbclient” with “smbclient.so” anymore.
Sorry i do not have a solution.
Perhaps you can read this
Part "Install php smbclient"
Perhaps you can only download “smbclient.so” and put it in the correct directory.