PHP Devs: Explain to me PHP 7's performance boost!

Hello, PHP community.

As you already know, PHP 7 offers a huge performance boost, whether it is the memory usage, or the requests per second (which is almost doubled).

Now, we know this is due to the new Zend Engine 3. Let me quote from the Rogue Wave (Zend) website :
"Thanks to the new Zend Engine 3.0, your apps see up to 2x faster performance and 50% better memory consumption than PHP 5.6, allowing you to serve more concurrent users without adding any hardware."

Can you guys explain to me, or at least find me references/articles/docs, what are the reasons that PHP 7 is that much better performing than PHP 5.6? What are those changes in Zend Engine 3 that make all the difference?

I'd appreciate both your explanations or any articles you can find for me to read.

Thanks!

Comments

[Pert Soomann]

This seems to be very in-depth video of how PHP5 works behind the curtains, and how PHP7 works with same code and how it makes the difference

[robencom]

Thanks for supplying with articles, I appreciate it, but I would also like your personal explanation, if you have one, or if it isn't much important to you to know such a thing, I'd appreciate also the reason behind that.

I am asking this question mainly because just yesterday I was asked about it in a job interview, and the interviewer kind of gave me "BS" answer/interpretation of their own, which now I realize was totally not based on facts, especially after reading couple of the articles shared by tux0r.

[robencom]

I think I've got the best reference now, so to answer my question:
PHP INTERNALS

But still, I really hoped a PHP developer would have explained this themselves..

[Oliver Köhler]

perhaps these slides will help

[Kyle Parisi]

I thought this talk was pretty informative by the creator himself.

[robencom]

Yeah I've been watching Rasmus's videos all morning. He kind of doesn't go into the details that I am requiring.