How to install php-xml on Ubuntu 16.04?

Question

I have php7.0 installed on Ubuntu 16.04 and I'm trying to install a forum software in apache2, but I get the following error:

In order to function correctly, the PHP XML/DOM extension needs to be available.

I tried to execute

sudo apt-get install php-xml
sudo apt-get install php7.0-xml

but these give me the following error:

php-xml: Depends: php7.1-xml but it is not going to be installed

When I try to install php7.1 from a PPA, I still get issues of dependencies from other PHP modules.

Any ideas how I can get php-xml installed without any dependency issues?

Answer 1