JpnForPhp\Helper\Helper::subString PHP Méthode

    public static function subString($str, $begin, $length)
    {
        return mb_substr($str, $begin, $length, 'UTF-8');
    }

 /**
  * Converts a year in Japanese format into Western format.
  *
  * @param $year : kanji or hiragana era name followed by digits, or era name in romaji, space and digit. I.e. : 明治33, めいじ33, Meiji 33
  * @return string|array : The year(s) in Western format.
  * @throws Exception
  */
 public static function toWesternYear($year)
 {
     if (Analyzer::hasKanji($year)) {
         $key = 'kanji';
         $eraName = Helper::extractKanji($year);
         $eraName = $eraName[0];
         $eraValue = (int) Helper::subString($year, Analyzer::length($eraName), Analyzer::length($year));
     } elseif (Analyzer::hasHiragana($year)) {
         $key = 'kana';
         $eraName = Helper::extractHiragana($year);
         $eraName = $eraName[0];
         $eraValue = (int) Helper::subString($year, Analyzer::length($eraName), Analyzer::length($year));
     } else {
         $key = 'romaji';
         $year = strtolower($year);
         $parts = explode(' ', $year);
         $eraName = $parts[0];
         $eraValue = (int) $parts[1];
     }
     if (empty($eraName) || empty($eraValue)) {
         throw new Exception('Invalid year ' . $year);
     }
     $max = count(self::$mapEras);
     $westernYears = array();
     for ($i = 0; $i < $max; $i++) {
         $era = self::$mapEras[$i];
         $overflown = false;
         if (strtolower($era[$key]) == $eraName) {
             $eraStart = $era['year'];
             $westernYear = $eraStart + $eraValue - 1;
             if ($i < $max - 1) {
                 $nextEra = self::$mapEras[$i + 1];
                 $nextEraYear = $nextEra['year'];
                 if ($westernYear > $nextEraYear) {
                     $overflown = true;
                 }
             }
             $westernYears[] = array('value' => $westernYear, 'overflown' => $overflown);
         }
     }
     $results = array();
     foreach ($westernYears as $westernYear) {
         if (!$westernYear['overflown']) {
             $results[] = $westernYear['value'];
         }
     }
     if (empty($results)) {
         throw new Exception('Year ' . $year . ' is invalid');
     } elseif (count($results) == 1) {
         return $results[0];
     } else {
         return $results;
     }
 }