title: create a nested JSON object with PHP
body: <p>What is the correct way to define this kind of JSON object in PHP</p>
  
  <pre><code>{
  "label": "Europe (EU27)",
  "data": [[1999, 3.0], [2000, 3.9], [2001, 2.0], [2002, 1.2], [2003, 1.3], [2004, 2.5], [2005, 2.0], [2006, 3.1], [2007, 2.9], [2008, 0.9]]
  }
  </code></pre>
  
  <p>I need to create a nested array that will be converted to JSON object via <code>json_encode()</code>.</p>