phpab: 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/phpab - from package: php-theseer-autoload

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

On Debian possible default full paths are:

/usr/bin/phpab - from package: phpab

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

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