title: Filters vs $_POST (or $_GET)
body: <p>Which one are you supposed to use, to check if a form submit button has been clicked?</p>
  
  <pre><code>&lt;input type="submit" name="action" value="Sign Up"&gt;
  </code></pre>
  
  <ol>
  <li><code>if (isset($_POST['action'] &amp;&amp; $_POST['action'] == "Sign Up") ...</code>
  or</li>
  <li><code>if (isset(filter_input(INPUT_POST, 'action')) &amp;&amp; filter_input(INPUT_POST, 'action') == "Sign Up")</code></li>
  </ol>
  
  <p>NB: I use $_POST['action] == 'Sign Up', because I use the 'action' array for delete and logout as well, and because some of my forms have two submit buttons, so I can differentiate).</p>