horde-sessions-gc: 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/horde-sessions-gc - from package: php-horde-horde

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

On Debian possible default full paths are:

/usr/bin/horde-sessions-gc - from package: php-horde

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

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