PHP use statements don't have to refer to existing classes

use-and-autoload.php

<?php
 
namespace Random\Example;

spl_autoload_register(function($class) {
    echo "Autoload triggered for class $class\n";
});

echo "Importing class with use upcoming...\n";
use Some\Example\Nonexistant\Class\Which\Will\Not\Trigger\The\Autoloader;
echo "use namespace done, autoloader not triggered so far\n";


echo "class_exists with autoloader upcoming...\n";
class_exists('Nonexistant');
echo "class_exisis with autoloader done\n";