$ sudo apt-get update
$ sudo apt-get install php-codesniffer 

php-codesniffer is installed in your system.

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

$ sudo dpkg-query -l | grep php-codesniffer *

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

php-codesniffer package basic information: