locale_get_plural

locale_get_plural($count, $langcode = NULL)

function locale_get_plural($count, $langcode = NULL) {
  $language_interface = \Drupal::languageManager()->getCurrentLanguage();

  // Used to store precomputed plural indexes corresponding to numbers
  // individually for each language.
  $plural_indexes = &drupal_static(__FUNCTION__ . ':plurals', array());

  $langcode = $langcode ? $langcode : $language_interface->getId();

  if (!isset($plural_indexes[$langcode][$count])) {
    // Retrieve and statically cache the plural formulas for all languages.
    $plural_formulas = \Drupal::service('locale.plural.formula')->getFormula($langcode);

    // If there is a plural formula for the language, evaluate it for the given
    // $count and statically cache the result for the combination of language
    // and count, since the result will always be identical.
    if (!empty($plural_formulas)) {
      // Plural formulas are stored as an array for 0-199. 100 is the highest
      // modulo used but storing 0-99 is not enough because below 100 we often
      // find exceptions (1, 2, etc).
      $index = $count > 199 ? 100 + ($count % 100) : $count;
      $plural_indexes[$langcode][$count] = isset($plural_formulas[$index]) ? $plural_formulas[$index] : $plural_formulas['default'];
    }
    // In case there is no plural formula for English (no imported translation
    // for English), use a default formula.
    elseif ($langcode == 'en') {
      $plural_indexes[$langcode][$count] = (int) ($count != 1);
    }
    // Otherwise, return -1 (unknown).
    else {
      $plural_indexes[$langcode][$count] = -1;
    }
  }
  return $plural_indexes[$langcode][$count];
}