sandbox_skeleton: 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/share/pear/data/symfony/bin/sandbox_skeleton - from package: php-symfony-symfony

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

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