code: public static function variablize($word)
      {
          $word = static::camelize($word);
  
          return mb_strtolower(mb_substr($word, 0, 1, self::encoding())) . mb_substr($word, 1, null, self::encoding());
      }
docs: Same as camelize but first char is in lowercase.
  
  Converts a word like "send_email" to "sendEmail". It
  will remove non alphanumeric character from the word, so
  "who's online" will be converted to "whoSOnline".
  @param string $word to lowerCamelCase
  @return string