vobjectvalidate: 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/vobjectvalidate - from package: php-sabre-vobject

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

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