Where to start when looking for guidance about learning to code for websites and how to make it secure

I am currently learning to code. I have always had an interest in making websites and one day would like to make a career out of it. Right now, I am learning HTML, PHP, MySQL/MariaDb, and have done a little C++. I was just wondering what other languages should I look at? I know there are many to choose from and I would like to learn about the more popular(widely used) languages.

Also, I wondered if anyone knows a good place to learn about how to secure your code (in any programming language). Things like cross site injection, sql injection, etc.. A couple of users on here have already given some advice; one about learning about SQL injection and another about learning prepared statements. I have briefly looked at PDO but haven't started using it in my code (probably should to get used to it). Like I said above, right now I am focusing on learning PHP and MySQL and would like a focus on that. Any other areas of secure coding that you think I should focus on, please let me know; if I want to turn this into a career, I should learn now.

So, if anyone has suggestions on where to start and what other areas you think I should also look at. My thoughts are that once you learn one language, it seems easier to pick up others. So far, I have some knowledge on the above topics but would always like to get better at it. It doesn't have to be an actual website/forum/etc. but just even a topic to look into.

Thanks for helping out.