title: Composer: file_put_contents(./composer.json): failed to open stream: Permission denied
body: <p>I'm trying to install <a href="https://github.com/hirak/prestissimo" rel="noreferrer">Prestissimo</a> to an Ubuntu 16.04 server, but that leads to an error:</p>
  
  <pre><code>$ composer global require "hirak/prestissimo:^0.3"
  Changed current directory to /home/kramer65/.composer
  
  
    [ErrorException]
    file_put_contents(./composer.json): failed to open stream: Permission denied
  
  
  require [--dev] [--prefer-source] [--prefer-dist] [--no-progress] [--no-update] [--no-scripts] [--update-no-dev] [--update-with-dependencies] [--ignore-platform-reqs] [--prefer-stable] [--prefer-lowest] [--sort-packages] [-o|--optimize-autoloader] [-a|--classmap-authoritative] [--] [&lt;packages&gt;]...
  </code></pre>
  
  <p>I'm logged in as user <code>kramer65</code>, so I wouldn't know why it can't write to my home folder. My normal reaction to a <code>permission denied</code> is to use <code>sudo</code>, but composer then always says:</p>
  
  <blockquote>
    <p>Do not run Composer as root/super user! See <a href="https://getcomposer.org/root" rel="noreferrer">https://getcomposer.org/root</a> for details</p>
  </blockquote>
  
  <p>Any idea how I can solve this?</p>