PHP 5 or PHP 7?

Question

What is the difference between PHP 5 and PHP 7?

Answer 1

You can read this for an answer
https://www.quora.com/What-are-the-major-difference-between-PHP-5-and-PHP-7

Basically it gained a huge performance improvement. ~50% which is the very reason to use it.
There is also the addition of new operators.
And some more...