title: Howto ubuntu 18.04 install / activate PHP extension ext-mcrypt
body: <p>I am installing a fresh kubuntu system 18.04, which is using by default php7.2</p>
  
  <p>A composer install for my current software project gibves me this error message: </p>
  
  <blockquote>
    <p>The requested PHP extension ext-mcrypt * is missing from your system.
    Install or enable PHP's mcrypt extension.</p>
  </blockquote>
  
  <p>Other than before there is no php-mcrypt available and other articles like this <a href="http://aryo.lecture.ub.ac.id/easy-install-php-mcrypt-extension-on-ubuntu-linux/" rel="nofollow noreferrer">http://aryo.lecture.ub.ac.id/easy-install-php-mcrypt-extension-on-ubuntu-linux/</a> don't help since an analog php-mcrypt or php7-mcrypt does not exists.</p>
  
  <p>How can I get a setup, which fulfills my requirement?</p>
  
  <pre><code>sudo apt-get install php7.2-ext-mcrypt
  </code></pre>
  
  <p>does not find an installation candidate.</p>
  
  <p>Is there a difference between php 7.1 and 7.2?</p>
  
  <p>not surprisingly this also does not do the trick:</p>
  
  <pre><code>$ sudo phpenmod mcrypt
  WARNING: Module mcrypt ini file doesn't exist under /etc/php/7.2/mods-available
  WARNING: Module mcrypt ini file doesn't exist under /etc/php/7.2/mods-available
  </code></pre>