src/AESGCM.php
private static function encryptWithPHP($K, $key_length, $IV, $P = null, $A = null, $tag_length = 128)
    {
        list($J0, $v, $a_len_padding, $H) = self::common($K, $key_length, $IV, $A);

        $C = self::getGCTR($K, $key_length, self::getInc(32, $J0), $P);
        $u = self::calcVector($C);
        $c_len_padding = self::addPadding($C);

        $S = self::getHash($H, $A.str_pad('', $v / 8, "\0").$C.str_pad('', $u / 8, "\0").$a_len_padding.$c_len_padding);
        $T = self::getMSB($tag_length, self::getGCTR($K, $key_length, $J0, $S));

        return [$C, $T];
    }
private static function encryptWithPHP($K, $key_length, $IV, $P = null, $A = null, $tag_length = 128)
    {
        list($J0, $v, $a_len_padding, $H) = self::common($K, $key_length, $IV, $A);

        $C = self::getGCTR($K, $key_length, self::getInc(32, $J0), $P);
        $u = self::calcVector($C);
        $c_len_padding = self::addPadding($C);

        $S = self::getHash($H, $A.str_pad('', $v / 8, "\0").$C.str_pad('', $u / 8, "\0").$a_len_padding.$c_len_padding);
        $T = self::getMSB($tag_length, self::getGCTR($K, $key_length, $J0, $S));

        return [$C, $T];
    }
@param string      $K          Key encryption key
@param string      $key_length Key length
@param string      $IV         Initialization vector
@param null|string $P          Data to encrypt (null for authentication)
@param null|string $A          Additional Authentication Data
@param int         $tag_length Tag length

@return array