php5dbg: 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/php5dbg - from package: php5-phpdbg

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

Error in other languages:
php5dbg: bevel nie gevind nie
php5dbg: comandă negăsită
php5dbg: comando não encontrado
php5dbg: commande introuvable
php5dbg: command not found
php5dbg: käsku ei ole
php5dbg: không tìm thấy lệnh
php5dbg: komanda nerasta
php5dbg: Kommando nicht gefunden.
php5dbg: kommandot finns inte
php5dbg: komut yok
php5dbg: nie znaleziono polecenia
php5dbg: níor aimsíodh an t-ordú
php5dbg: no se encontró la orden
php5dbg: no s'ha trobat l'ordre
php5dbg: opdracht niet gevonden
php5dbg: parancs nem található
php5dbg: perintah tidak ditemukan
php5dbg: príkaz nenájdený
php5dbg: příkaz nenalezen
php5dbg: команда не найдена
php5dbg: командата не е открита
php5dbg: 命令找不到
php5dbg: コマンドが見つかりません