how to setup yum and install php-domxml

[ZaNaToS]

Hello

I have an centos 3.3 server and I want to install php-domxml (my php is 4.4.0)
I run the command: yum install yum install php-domxml
and I get:
[root@web etc]# yum install php-domxml
Gathering header information file(s) from server(s)
Server: CentOS-3 - Addons
Server: CentOS-3 - Base
Server: CentOS-3 - Extras
Server: CentOS-3 - Updates
Finding updated packages
Downloading needed headers
Cannot find a package matching php-domxml
No actions to take

I also run: [root@web etc]# yum list php-domxml
Gathering header information file(s) from server(s)
Server: CentOS-3 - Addons
Server: CentOS-3 - Base
Server: CentOS-3 - Extras
Server: CentOS-3 - Updates
Finding updated packages
Downloading needed headers
Looking in Available Packages:
Name Arch Version Repo
--------------------------------------------------------------------------------

Looking in Installed Packages:
Name Arch Version Repo
--------------------------------------------------------------------------------


how can I install php-domxml ?
my php was installed by art's repo.