kde4-config: 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/kde4-config - from package: kdelibs

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

On Debian possible default full paths are:

/usr/bin/kde4-config - from package: kdelibs-bin

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

Error in other languages:
kde4-config: bevel nie gevind nie
kde4-config: comandă negăsită
kde4-config: comando não encontrado
kde4-config: commande introuvable
kde4-config: command not found
kde4-config: käsku ei ole
kde4-config: không tìm thấy lệnh
kde4-config: komanda nerasta
kde4-config: Kommando nicht gefunden.
kde4-config: kommandot finns inte
kde4-config: komut yok
kde4-config: nie znaleziono polecenia
kde4-config: níor aimsíodh an t-ordú
kde4-config: no se encontró la orden
kde4-config: no s'ha trobat l'ordre
kde4-config: opdracht niet gevonden
kde4-config: parancs nem található
kde4-config: perintah tidak ditemukan
kde4-config: príkaz nenájdený
kde4-config: příkaz nenalezen
kde4-config: команда не найдена
kde4-config: командата не е открита
kde4-config: 命令找不到
kde4-config: コマンドが見つかりません