title: Why did smarty registerPlugin() stop workgin somewhere around v3.1.30?
body: <p>I migrated from smarty <code>v3.1.29</code> to <code>v3.1.33</code> and my registered plugins stopped working. Why?</p>
  
  <p>I used this syntax:</p>
  
  <pre><code>$this -&gt; registerPlugin ( "function", "tpl_func", "php_func" );
  </code></pre>
  
  <p>The behaviour goes wrong only with <code>php 7.0</code>. With <code>php 7.3.14</code> it still works fine.</p>