Class 'XMLWriter' not found

In a Red Hat or CentOS server installation, XMLwriter may not be enabled by default. To enable it, follow these steps:

# If you are using the base 5.1.6 php, then
yum -y install php-xml

#if you are using php 5.2 (from the centos 5 testing repo)
yum -y --enablerepo=c5-testing install php-xml

#restart apache
service httpd restart