Java new byte[16] same as str_repeat(“\0”, 16) in PHP!



class CryptAES
{
    protected $cipher = MCRYPT_RIJNDAEL_128;
    protected $mode   = MCRYPT_MODE_CBC;
    protected $pad_method = NULL;
    protected $secret_key = '';
    protected $iv = '';

    public function set_cipher($cipher)
    {
        $this -> cipher = $cipher;
    }

    public function set_mode($mode)
    {
        $this -> mode = $mode;
    }

    public function set_iv($iv)
    {
        $this -> iv = $iv;
    }

    public function set_key($key)
    {
        $this -> secret_key = $key;
    }

    public function require_pkcs5()
    {
        $this -> pad_method = 'pkcs5';
    }

    protected function pad_or_unpad($str, $ext)
    {
        if ( is_null($this -> pad_method) )
        {
            return $str;
        }
        else
        {
            $func_name = __CLASS__ . '::' . $this->pad_method . '_' . $ext . 'pad';
            if ( is_callable($func_name) )
            {
                $size = mcrypt_get_block_size($this->cipher, $this->mode);
                return call_user_func($func_name, $str, $size);
            }
        }
        return $str;
    }

    protected function pad($str)
    {
        return $this->pad_or_unpad($str, '');
    }

    protected function unpad($str)
    {
        return $this->pad_or_unpad($str, 'un');
    }

    public function encrypt($str)
    {
        $str = $this -> pad($str);
        $td = mcrypt_module_open($this->cipher, '', $this->mode, '');

        if ( empty($this->iv) )
        {
            //$iv = @mcrypt_create_iv(mcrypt_enc_get_iv_size($td), MCRYPT_RAND);
            $iv = str_repeat("\0", mcrypt_enc_get_iv_size($td));                // < << like here
        }
        else
        {
            $iv = $this->iv;
        }

        mcrypt_generic_init($td, $this->secret_key, $iv);
        $cyper_text = mcrypt_generic($td, $str);
        $rt = base64_encode($cyper_text);
        mcrypt_generic_deinit($td);
        mcrypt_module_close($td);

        return $rt;
    }

    public function decrypt($str)
    {
        $td = mcrypt_module_open($this->cipher, '', $this->mode, '');

        if ( empty($this->iv) )
        {
            //$iv = @mcrypt_create_iv(mcrypt_enc_get_iv_size($td), MCRYPT_RAND);
            $iv = str_repeat("\0", mcrypt_enc_get_iv_size($td));
        }
        else
        {
            $iv = $this->iv;
        }

        mcrypt_generic_init($td, $this->secret_key, $iv);
        $decrypted_text = mdecrypt_generic($td, base64_decode($str));
        $rt = $decrypted_text;
        mcrypt_generic_deinit($td);
        mcrypt_module_close($td);

        return $this -> unpad($rt);
    }

    public static function pkcs5_pad($text, $blocksize)
    {
        $pad = $blocksize - (strlen($text) % $blocksize);
        $text .= str_repeat(chr($pad), $pad);
        return $text;
    }

    public static function pkcs5_unpad($text)
    {
        $pad = ord($text{strlen($text) - 1});
        if ($pad > strlen($text)) return false;
        if (strspn($text, chr($pad), strlen($text) - $pad) != $pad) return false;
        return substr($text, 0, -1 * $pad);
    }

}