If you ask this question I think it is ia good time to rent some super minimal VPS (you can get it for free at amazon) and setup and rebuild the server from scratch several times. Then you definitely know a bit more about linux. It is like learning how to ride a bicycle as a kid. All mentioned distributions are good. What you need is:
- webserver (nginx or apache)
- php (php-fpm if you use nginx)
- database (mysql or mariadb)
CentOS does not provide php out-of-the-box, I am unsure about nginx. debian (and ubuntu which relies on "debian testing") provides php as well as nginx out-of-the-box. All distributions provide mysql, from what I know, you need to install a repository for mariadb.
Debian 7 is outdated, I would get Debian 9.