title: Convert date string with timezone to timestamp
body: <p>I receive dates in the following format <code>2015-01-09T20:46:00+0100</code> and need to convert it in timestamp.
  Unfortunately, strtotime function is ignoring the timezone component :</p>
  
  <pre><code>print strtotime('2015-01-09T20:46:00+0100') . "\n";
  print strtotime('2015-01-09T20:46:00');
  
  //result is the same with or without timezone:
  //1420832760
  //1420832760
  </code></pre>
  
  <p>What is the right way to solve this issue ?</p>