How to make valid phar file? (Hello.php puts in hello directory.)

Hello.php

<?php

class Hello {
  public function sayHello() {
    echo "hello\n";
  }
}

make_phar.php

<?php

$phar = new Phar('hello.phar', 0, 'hello.phar');
$phar->buildFromDirectory(__DIR__ . '/hello');
$phar->setDefaultStub();

open_phar.php

<?php

try {
  $file = (new PharFileInfo('phar://' . __DIR__ . '/hello.phar/hello/Hello.php'))->openFile();
  var_dump($file);
} catch (Exception $e) {
  var_dump($e);
}

I don't understand how to take the files from an updated plugin and make it into a .phar file on my server. Plz help