title: Inline PHP (command line)
body: <p>I would like to make something like <em>tryruby.org</em>. I take a line from the user (e.g., <code>echo __FILE__</code>) and I want to execute it in PHP and return the output back to the client.</p>
  <p>I tried to do <code>exec('php -r ' . $command, $output)</code>, but <code>$output</code> always contains the PHP help section.</p>
  <p>How can I implement this feature?</p>