title: Wrong result when pass html select value to use with timezone_set
body: <p>I'm making a little system for our team that generate some titles for use in tickets. I'm having a problem with the final expression here:</p>
  
  <pre><code>$horaBrasilAgora = $horaEntrada;
  
  date_default_timezone_set("Asia/Dubai");
  $horaLocalidadeAgora = date('H');
  
  $diferenca = $horaLocalidadeAgora - $horaBrasilAgora;
  return $diferenca;
  </code></pre>
  
  <p>The above result is OK, it returns "7". But, if I take the timezone_set by a variable that comes from HTML select value, it returns incorretly.</p>
  
  <pre><code>$horaBrasilAgora = $horaEntrada;
  
  date_default_timezone_set($timezone);
  $horaLocalidadeAgora = date('H');
  
  $diferenca = $horaLocalidadeAgora - $horaBrasilAgora;
  return $diferenca;
  </code></pre>
  
  <p>It returns "4". Here is my select html form:</p>
  
  <pre><code>&lt;!-- Select Basic --&gt;
  &lt;div class="form-group"&gt;
  &lt;label class="col-md-4 control-label" for="timezone"&gt;Fuso Horário&lt;/label&gt;
  &lt;div class="col-md-4"&gt;
      &lt;select id="timezone" name="timezone" class="form-control"&gt;
      &lt;option value="Asia/Dubai"&gt;Abu Dhabi&lt;/option&gt;
      &lt;option value="America/Argentina/Buenos_Aires"&gt;Arroyo Seco&lt;/option&gt;
  </code></pre>
  
  <p>[...] and rest of code. I think the problem may be with the "value" field, where I don't know if the "/" can be the problem.</p>
  
  <p>I'm really confuse about what's happening.</p>