title: unset form submit button
body: <pre><code>&lt;body&gt;
  
  &lt;?php
  
  if(isset($_POST['vendor_add_submit'])){
  
  //INSERT INTO DB
  
  unset(  $_POST['vendor_add_submit'] );
  }
  
  ?&gt;
  
  
  &lt;form method="post" action="&lt;?php echo $_SERVER['PHP_SELF'] ?&gt;" &gt;
  
  
  &lt;label&gt;Email&lt;/label&gt;
  &lt;input type="text" name="vendor_email" value="" /&gt;
  
  
  &lt;input type="submit" name="vendor_add_submit" value="SAVE" /&gt;
  
  
  &lt;/form&gt;
  &lt;/body&gt;
  </code></pre>
  
  <p><code>unset(  $_POST['vendor_add_submit'] );</code> is used to prevent more than one time insertion into db on page refresh. I tested with <code>print_r($_POST['vendor_add_submit'] )</code> before and after the unset and found that the <code>unset()</code> function does not work. </p>
  
  <p>How can I achieve the purpose of the unset function, plz?</p>