-S, --sparse Try to handle sparse files efficiently so they take up less space on the destination. Conflicts with --inplace because it's not possible to overwrite data in a sparse fashion. NOTE: Don't use this option when the destination is a Solaris “tmpfs” filesystem. It doesn't seem to handle seeks over null regions correctly and ends up corrupting the files.
Похоже, вы используете репозиторий Webtatic, попробуйте следующее:
# yum --enablerepo=webtatic install php-xml