php写的AES加密解密类分享

<"\0");
	}

	/**
	 * Returns the length of the given string.
	 * If available uses the multibyte string function mb_strlen.
	 * @param string $string the string being measured for length
	 * @return integer the length of the string
	 */
	private static function strlen($string)
	{
		return extension_loaded('mbstring') ? mb_strlen($string,'8bit') : strlen($string);
	}

	/**
	 * Returns the portion of string specified by the start and length parameters.
	 * If available uses the multibyte string function mb_substr
	 * @param string $string the input string. Must be one character or longer.
	 * @param integer $start the starting position
	 * @param integer $length the desired portion length
	 * @return string the extracted part of string, or FALSE on failure or an empty string.
	 */
	private static function substr($string,$start,$length)
	{
		return extension_loaded('mbstring') ? mb_substr($string,$start,$length,'8bit') : substr($string,$start,$length);
	}
}