title: Enabling php ext-xml?
body: <p>While trying to use Composer to create a Symfony 4 project I got the following error:</p>
  
  <pre><code>steve@laptop ~ $ php composer.phar create-project symfony/skeleton my-proj
  Installing symfony/skeleton (v4.0.0)
    - Installing symfony/skeleton (v4.0.0): Loading from cache
  Created project in my-proj
  Loading composer repositories with package information
  Updating dependencies (including require-dev)
  Your requirements could not be resolved to an installable set of packages.
  
    Problem 1
      - symfony/framework-bundle v4.0.1 requires ext-xml * -&gt; the requested PHP extension xml is missing from your system.
      - symfony/framework-bundle v4.0.0 requires ext-xml * -&gt; the requested PHP extension xml is missing from your system.
      - Installation request for symfony/framework-bundle ^4.0 -&gt; satisfiable by symfony/framework-bundle[v4.0.0, v4.0.1].
  
    To enable extensions, verify that they are enabled in your .ini files:
      - /etc/php/7.2/cli/php.ini
      - /etc/php/7.2/cli/conf.d/10-opcache.ini
      - /etc/php/7.2/cli/conf.d/10-pdo.ini
      - /etc/php/7.2/cli/conf.d/20-calendar.ini
      - /etc/php/7.2/cli/conf.d/20-ctype.ini
      - /etc/php/7.2/cli/conf.d/20-exif.ini
      - /etc/php/7.2/cli/conf.d/20-fileinfo.ini
      - /etc/php/7.2/cli/conf.d/20-ftp.ini
      - /etc/php/7.2/cli/conf.d/20-gettext.ini
      - /etc/php/7.2/cli/conf.d/20-iconv.ini
      - /etc/php/7.2/cli/conf.d/20-json.ini
      - /etc/php/7.2/cli/conf.d/20-phar.ini
      - /etc/php/7.2/cli/conf.d/20-posix.ini
      - /etc/php/7.2/cli/conf.d/20-readline.ini
      - /etc/php/7.2/cli/conf.d/20-shmop.ini
      - /etc/php/7.2/cli/conf.d/20-sockets.ini
      - /etc/php/7.2/cli/conf.d/20-sysvmsg.ini
      - /etc/php/7.2/cli/conf.d/20-sysvsem.ini
      - /etc/php/7.2/cli/conf.d/20-sysvshm.ini
      - /etc/php/7.2/cli/conf.d/20-tokenizer.ini
    You can also run `php --ini` inside terminal to see which files are used by PHP in CLI mode.
  steve@laptop ~ $ php --ini
  
      steve@laptop ~ $ php --version
          PHP 7.2.0-2+ubuntu16.04.1+deb.sury.org+2 (cli) (built: Dec  7 2017 20:14:31) ( NTS )
         Copyright (c) 1997-2017 The PHP Group
          Zend Engine v3.2.0, Copyright (c) 1998-2017 Zend Technologies
          with Zend OPcache v7.2.0-2+ubuntu16.04.1+deb.sury.org+2, Copyright (c) 1999-2017, by Zend Technologies
      steve@laptop ~ $ sudo apt-get install php-xml
          [sudo] password for steve: 
          Reading package lists... Done
          Building dependency tree       
          Reading state information... Done
          php-xml is already the newest version (1:7.1+55+ubuntu16.04.1+deb.sury.org+1).
          0 to upgrade, 0 to newly install, 0 to remove and 253 not to upgrade.
  </code></pre>
  
  <p>I did search in php.ini for ext-xml to see if I could uncomment it in order to enable it but I did not find any mention of ext-xml. I have not searched anywhere else because I am very unsure about what I am doing.</p>
  
  <p>Any help would be very much appreciated, Steve</p>