title: php 5.5 sorting array by value and subvalue
body: <p>I have a working sorting code in PHP 7</p>
  
  <pre><code>usort($ferr, function($a, $b) {
      $retval = $b['value'] &lt;=&gt; $a['value'];
      if($retval == 0) {
          $retval = $b['subvalue'] &lt;=&gt; $a['subvalue'];    
      }
      return $retval;
  });
  </code></pre>
  
  <p>but <code>PHP 5.5</code> doesn't support the <code>&lt;=&gt;</code> operator. It only supports <code>-</code> operator, which doesn't work in this case. How can it be done in <code>PHP 5.5</code> ?
  Thanks for help.</p>