$stmt_user = $mysqli->prepare("
            #Insert User row
            INSERT INTO
             `USER`
            (
             `name`,
             `contactNumber`,
             `email`,
             `password`,
             `salt`,
             `gender`
            )
            VALUES
            (
             ?,#name
             ?,#contactNumber
             ?,#email
             ?,#password
             ?,#salt
             ?#gender
            )
            ") or trigger_error(mysql_error());
        $stmt_get_user_id = $mysqli->prepare("
            #get id of last inserted user
            SELECT
            `id`
            FROM
            `USER`
            ORDER BY
            `id`
            DESC
            LIMIT
            1
            ") or trigger_error(mysql_error());
        $stmt_address = $mysqli->prepare("
            #insert Address
            INSERT
            INTO
            `ADDRESS`
            (
            `lineOne`,
            `postcode`
            )
            VALUES
            (
            ?,#lineOne
            ? #postcode
            )
            ") or trigger_error(mysql_error());
        $stmt_get_address_id = $mysqli->prepare("
            #get id of last inserted address
            SELECT
            `id`
            FROM
            `USER`
            ORDER BY
            `id`
            DESC
            LIMIT
            1
            ") or trigger_error(mysql_error());
        $stmt_user_address = $mysqli->prepare("
            INSERT
            INTO
            `USER_ADDRESS`
            (
            `USER_id`,
            `ADDRESS_id`
            )
            VALUES
            (
            ?,#USER_id
            ? #ADDRESS_id
            )
            ") or trigger_error(mysql_error());
        $stmt_user_group = $mysqli->prepare("
            INSERT
            INTO
            `USER_GROUP`
            (
            `USER_id`,
            `GROUP_id`
            )
            VALUES
            (
            ?,#USER_id
            ? #GROUP_id
            )
            ") or trigger_error(mysql_error());

                $stmt_user->bind_param("ssssss", $name, $contactNumber, $email, $password, $salt, $gender) or trigger_error(mysql_error());
                $stmt_get_user_id->bind_result($USER_id) or trigger_error(mysql_error());
                $stmt_user->execute() or trigger_error(mysql_error());
                $stmt_get_user_id->execute() or trigger_error(mysql_error());
                $stmt_get_user_id->store_result() or trigger_error(mysql_error());
                $stmt_get_user_id->fetch() or trigger_error(mysql_error());
                $stmt_address->bind_param("ss", $lineOne, $postcode) or trigger_error(mysql_error());
                $stmt_address->execute() or trigger_error(mysql_error());
                $stmt_get_address_id->bind_result($ADDRESS_id) or trigger_error(mysql_error());
                $stmt_get_address_id->execute() or trigger_error(mysql_error());
                $stmt_get_address_id->store_result() or trigger_error(mysql_error());
                $stmt_get_address_id->fetch() or trigger_error(mysql_error());
                $stmt_user_address->bind_param("ii", $USER_id, $ADDRESS_id) or trigger_error(mysql_error());
                $stmt_user_address->execute() or trigger_error(mysql_error());
                $stmt_user_group->bind_param("ii", $USER_id, 1) or trigger_error(mysql_error());
                $stmt_user_group->execute() or trigger_error(mysql_error());