Just like how WordPress follows a set of coding standards, PHP has its own coding standards. Since WordPress is primarily based on PHP, following these coding standards is a must if you want to develop reliable web applications.
You can use PHP_CodeSniffer to check your code against defined coding standards and get alerted you if there are any violations.
If you are not sure if you had installed PHPCS previously, you can check your system by running the which phpcs command. It should return the path of the current PHPCS installation. If nothing was returned, then you probably haven’t installed phpcs before.
You can find the version of PHPCS you are running by running phpcs --version.
Assuming you have PHP and Composer already installed,
Go to composer dir cd ~/.composer
composer global require "squizlabs/php_codesniffer=*"
If you have PHPCS already installed, you can run composer update squizlabs/php_codesniffer to update it.
And you can check the version by running ./vendor/bin/phpcs --version
Add ~/.composer/vendor/bin to $PATH in .bashrc or .zshrc and reload the terminal or open a new tab.
curl -OL https://squizlabs.github.io/PHP_CodeSniffer/phpcs.phar && chmod +x phpcs.phar && mv phpcs.phar /usr/local/bin/phpcs
curl -OL https://squizlabs.github.io/PHP_CodeSniffer/phpcbf.phar && chmod +x phpcbf.phar && mv phpcbf.phar /usr/local/bin/phpcbf
You can also change /usr/local/bin/ to a custom path like ~/.bin and add that custom path to $PATH as mentioned above in the Composer Install/Update section.