题目提示想想初始页面是哪个
    于是尝试访问index.php，但是又重定向到1.php页面，接着用浏览器抓包看看
    于是在index.php的重定向页面的响应头中看到flag

    1. HTTP/1.1 302 Found
    2. Date: Tue, 24 Nov 2020 09:20:49 GMT
    3. Server: Apache/2.4.38 (Debian)
    4. X-Powered-By: PHP/7.2.21
    5. FLAG: flag{very_baby_web}
    6. Location: 1.php
    7. Content-Length: 17
    8. Keep-Alive: timeout=5, max=100
    9. Connection: Keep-Alive
    10. Content-Type: text/html; charset=UTF-8