changelog.php: 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/changelog.php - from package: php-symfony-symfony

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

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