title: Does PHP's spl_autoload_register Load Only Necessary Classes?
body: <p>I've found numerous stackoverflow pages claiming that spl_autoload_register only loads necessary classes (<a href="https://stackoverflow.com/questions/6437134/autoload-vs-include-family/6437316#6437316">__autoload vs include family</a> for example), but is there documentation or proof of this? I checked php.net and couldn't find anything in their documentation. I also did a Google search and couldn't find an official answer.</p>