Server :: Yum Update PHP On CentOS - Missing Dependency Php-common?

I am trying to update PHP on a centos server by using

Code:

yum update php which results in the following...

Code:

Setting up Update Process
Setting up repositories
plesk 100% |=========================| 951 B 00:00
update 100% |=========================| 951 B 00:00

[code]....

Error: Missing Dependency: php-common = 5.2.9-1.el4.art is needed by package php-xml I think PHP was previously updated using the centosplus repository which may be causing this problem. yum install php-common results in a nothing to do error.