title: Travis CI: PHP 7.2 don't support Argon2i
body: <p>I've an error in my project with Travis CI:</p>
  
  <blockquote>
    <p>Argon2i algorithm is not supported. Please install the libsodium extension<br>
      or upgrade to PHP 7.2+. </p>
  </blockquote>
  
  <p>But, Argon2i is present in the PHP 7.2 version and Travis CI install the PHP 7.2 version:</p>
  
  <pre><code>$ phpenv global 7.2 2&gt;/dev/null
  
  7.2 is not pre-installed; installing
  Downloading archive: https://s3.amazonaws.com/travis-php-archives/binaries/ubuntu/14.04/x86_64/php-7.2.tar.bz2
  $ curl -s -o archive.tar.bz2 $archive_url &amp;&amp; tar xjf archive.tar.bz2 --directory /
  
  $ phpenv global 7.2
  
  $ php --version
  PHP 7.2.0 (cli) (built: Dec  2 2017 17:12:55) ( ZTS )
  Copyright (c) 1997-2017 The PHP Group
  Zend Engine v3.2.0, Copyright (c) 1998-2017 Zend Technologies
      with Zend OPcache v7.2.0, Copyright (c) 1999-2017, by Zend Technologies
      with Xdebug v2.6.0-dev, Copyright (c) 2002-2017, by Derick Rethans
  </code></pre>
  
  <p>Someone have an idea ?</p>