phpcs: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/phpcs - from package: php-pear-PHP-CodeSniffer

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/phpcs - from package: php-codesniffer

You may install the required package with command apt-get install {package}

Error in other languages:
phpcs: bevel nie gevind nie
phpcs: comandă negăsită
phpcs: comando não encontrado
phpcs: commande introuvable
phpcs: command not found
phpcs: käsku ei ole
phpcs: không tìm thấy lệnh
phpcs: komanda nerasta
phpcs: Kommando nicht gefunden.
phpcs: kommandot finns inte
phpcs: komut yok
phpcs: nie znaleziono polecenia
phpcs: níor aimsíodh an t-ordú
phpcs: no se encontró la orden
phpcs: no s'ha trobat l'ordre
phpcs: opdracht niet gevonden
phpcs: parancs nem található
phpcs: perintah tidak ditemukan
phpcs: príkaz nenájdený
phpcs: příkaz nenalezen
phpcs: команда не найдена
phpcs: командата не е открита
phpcs: 命令找不到
phpcs: コマンドが見つかりません