utf8_(en|de)code removed from php7?

I had the same problem. Just install php7.0-xml package. Ubuntu 16.04:

sudo apt-get install php7.0-xml

Edit: Restart apache2 to load the new package.

On Ubuntu, you got the following message during the upgrade of PHP7:

php7.0 (7.0.3-6) unstable; urgency=medium

  * Several extensions have been split into separate extension packages:
   - php-dba - Database (dbm-style) Abstraction Layer
   - php-mbstring - Multibyte String
   - php-soap - SOAP
   - php-xml - DOM, SimpleXML, WDDX, XML, XMLReader and XMLWriter
   - php-zip - Zip
  * The new packages are not installed automatically, so you will need to
    install them by hand, if you use the functions in those modules.
  * Most modules that have been builtin before are now included in
    php7.0-common package and they are enabled by default for your
    convenience.  You can disable unneede modules via phpdismod tool.

 -- Ondřej Surý <[email protected]>  Mon, 22 Feb 2016 12:37:09 +0100

so it's one of those packages that's causing the problem. In this case, it's php-xml.

Note the

The new packages are not installed automatically

You can fix that by

sudo apt-get install php-xml
sudo apache2ctl graceful