Why is this extension not available in ubuntu 16?

Question

symfony

As it is, everywhere they write that simplexml_import_dom () and the SimpleXML extension are available in php out of the box. php version

[email protected]:~# php -v
PHP 7.0.8-0ubuntu0.16.04.1 (cli) ( NTS )
Copyright (c) 1997-2016 The PHP Group
Zend Engine v3.0.0, Copyright (c) 1998-2016 Zend Technologies
    with Zend OPcache v7.0.8-0ubuntu0.16.04.1, Copyright (c) 1999-2016, by Zend Technologies

Answer 1

Like so, everywhere they write that simplexml_import_dom () and the SimpleXML extension are available in php out of the box

In some discussions, they write that since php 7.0.3 SimpleXML is missing out of the box. Try to put separately
apt-get install php7.0-xml