title: When a checkbox is unchecked I want to show all data from the database
body: <p>I want to make a search with checkboxes. It works when the checkboxes are selected but does not show anything when unchecked. I want to show all the data from database when the checkbox is unchecked</p>
  
  <pre><code>$single = isset($_REQUEST['single']) ? 'Single' : '';
  $married = isset($_REQUEST['married']) ? 'Married' : '';
  
  SELECT *
  FROM $users_table
  WHERE (civil_status = '$single' OR civil_status = '$married')
  
  &lt;input type="checkbox" name = "single"&gt;
  &lt;label class="label-for-checkbox" &gt;Single&lt;/label&gt;
  &lt;input type="checkbox" name = "married"&gt;
  &lt;label class="label-for-checkbox" &gt;Married&lt;/label&gt;
  </code></pre>
  
  <p>In the database there is a column named 'civil status' which has ENUM value 'Single', 'Married'.</p>
  
  <p>There are 2 checkboxes married and single. When I select married checkbox only list of people who are married displays. When I select single only list of single people displays. When both are selected it displays both results. But, when both of them are unchecked I want to show all married and single people.</p>