httpd.worker: 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/sbin/httpd.worker - from package: httpd

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

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