$ sudo apt-get update
$ sudo apt-get install php-crypt-cbc 

php-crypt-cbc is installed in your system.

Make ensure the php-crypt-cbc package were installed using the commands given below,

$ sudo dpkg-query -l | grep php-crypt-cbc *

You will get with php-crypt-cbc package name, version, architecture and description in a table

php-crypt-cbc package basic information: