Within an extension how can load a custom `Civi` name-spaced class?
Add the following elements to your extension's info.xml file to enable PSR-4 autoloading:

&lt;classloader&gt;
  &lt;psr4 prefix="Civi\" path="Civi"/&gt;
&lt;/classloader&gt;


Also see docs on the &lt;classloader&gt; element