php5-cgi: 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 Debian possible default full paths are:

/usr/bin/php5-cgi - from package: php5-cgi

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

Error in other languages:
php5-cgi: bevel nie gevind nie
php5-cgi: comandă negăsită
php5-cgi: comando não encontrado
php5-cgi: commande introuvable
php5-cgi: command not found
php5-cgi: käsku ei ole
php5-cgi: không tìm thấy lệnh
php5-cgi: komanda nerasta
php5-cgi: Kommando nicht gefunden.
php5-cgi: kommandot finns inte
php5-cgi: komut yok
php5-cgi: nie znaleziono polecenia
php5-cgi: níor aimsíodh an t-ordú
php5-cgi: no se encontró la orden
php5-cgi: no s'ha trobat l'ordre
php5-cgi: opdracht niet gevonden
php5-cgi: parancs nem található
php5-cgi: perintah tidak ditemukan
php5-cgi: príkaz nenájdený
php5-cgi: příkaz nenalezen
php5-cgi: команда не найдена
php5-cgi: командата не е открита
php5-cgi: 命令找不到
php5-cgi: コマンドが見つかりません