How to execute this function?

function drupal_bootstrap($phase) {
  static $phases = array(DRUPAL_BOOTSTRAP_CONFIGURATION, DRUPAL_BOOTSTRAP_EARLY_PAGE_CACHE, DRUPAL_BOOTSTRAP_DATABASE, DRUPAL_BOOTSTRAP_ACCESS, DRUPAL_BOOTSTRAP_SESSION, DRUPAL_BOOTSTRAP_LATE_PAGE_CACHE, DRUPAL_BOOTSTRAP_LANGUAGE, DRUPAL_BOOTSTRAP_PATH, DRUPAL_BOOTSTRAP_FULL), $phase_index = 0;

  while ($phase >= $phase_index && isset($phases[$phase_index])) {
    $current_phase = $phases[$phase_index];
    unset($phases[$phase_index++]);
    _drupal_bootstrap($current_phase);
  }
}

now,if i use this drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL); what result will be return. the thing that confused me is in the above function,there is no return. another is if the argument is DRUPAL_BOOTSTRAP_FULL, there will be this

DRUPAL_BOOTSTRAP_FULL=array(DRUPAL_BOOTSTRAP_CONFIGURATION, DRUPAL_BOOTSTRAP_EARLY_PAGE_CACHE, DRUPAL_BOOTSTRAP_DATABASE, DRUPAL_BOOTSTRAP_ACCESS, DRUPAL_BOOTSTRAP_SESSION, DRUPAL_BOOTSTRAP_LATE_PAGE_CACHE, DRUPAL_BOOTSTRAP_LANGUAGE, DRUPAL_BOOTSTRAP_PATH, DRUPAL_BOOTSTRAP_FULL),

this give the array to the variable DRUPAL_BOOTSTRAP_FULL. i feel it useless? thank you.

i am sorry i made an error.

What? :shifty:
The argument is called $phase.
The array is called $phases.
They’re not the same.