title: html - select option not selected by user - validation
body: <p>This is the script i am using for select a city. But the user proceeded without any selection from the list.</p>
  
  <pre><code>&lt;select&gt;
  &lt;option disabled selected value&gt; -- select an option -- &lt;/option&gt;
  &lt;option&gt;City 1&lt;/option&gt;
  &lt;option&gt;City 2&lt;/option&gt;
  &lt;option&gt;City 3&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>After user Submits the form, errors comes like "Notice: Undefined index: CITY in /home/...../public_html/address.php on line 44
  Column 'CITY' cannot be null"</p>
  
  <p>How to validate it before Submit the form?</p>