title: PHP Fatal error: Interface 'JsonSerializable'
body: <p>I'm trying to install Magento2 on a new server LAMP setup. I am running the following:</p>
  
  <ul>
  <li>Ubuntu Server 16.04</li>
  <li>PHP 7.0</li>
  <li>Apache 2.4</li>
  </ul>
  
  <p>I keep getting a 500 error and when I refer to the logs I can see <code>PHP Fatal error:  Interface 'JsonSerializable' Not Found</code>.</p>
  
  <p>I have tried running <code>apt-get install php-json</code> and restarting Apache but this doesn't work. I have also tried enabling JSON using <code>a2enmod json</code> but i get an error saying the module doesn't exist.</p>
  
  <p>I have been as far as page 3 on Google and found nothing that helps. Can anyone come up with something that I haven't already? I am officially at a loss.</p>