通过选择下拉菜单过滤mysql结果。

I'm a new member of StackOverflow, and although I've been using the website for a long time, it's my first time posting a question, in a hope that someone will be able to help me. I'll start by saying that my knowledge of PHP and MySQL is basic, but what I'm trying to do isn't too complex in my opinion, so hopefully I won't be asking for much. I've done a lot of prior research, but I just couldn't find the right answer.I'm a new member of StackOverflow, and although