Drop Support for PHP 7

[sprankhub]

I suggest fully dropping support for PHP 7 by removing all PHP 7 related files and codes in this repository. PHP 7 is EOL since forever. I don't see a reason to keep it. It takes time to maintain it, it needs computing power etc.

Are you guys fine with this, @jissereitsma @fredden @convenient @amenk?

[convenient]

PHP 7?!

[jissereitsma]

I would say it is good to remove it.

[fredden]

I think it's fair for this repository to drop support for PHP < 8.0.