Wouldn't that make debugging much much easier? Since you get a clean slate for every request, bugs can now be tracked and replicated in a saner way. I personally prefer this method for building and maintaining a huge and complex application despite knowing that it may not be an efficient one.
Without a heavy framework, you get the best of both worlds.
It's called the "shared nothing architecture", and its by design. Nothing is shared between requests, so why _not_ tear down?
That model actually has a lot of benefits for web applications (it scales very well), and I consider it one of PHP's strong points.
Is Laravel really a Rails clone? I thought that was Symfony. I honestly don't understand why the most popular PHP frameworks are all Rails clones. In my own work, I made things more in a PHP style than Ruby.
The current implementation uses shared memory.
In addition, that does not mean retaining all the variables and data, only the compiled opcodes and that's the bulk of the startup time.
I've been a PHP dev for 15 years and the biggest issue with frameworks in PHP is PHP itself. A request comes in, the PHP process loads up everything, executes the request and tears down...on every single request.
In just about every other language, the application boots up, loads everything into RAM and each individual request doesn't have to reload things.
There are definitely trade offs here. You can have a 1 TB hard drive filled up with PHP code on a 256mb of RAM server and everything is still going to run fine. There's a lot of value in that and most people who are PHP averse seem to be turning to Lamba from AWS to fill that gap. PHP scales down better than just about anything else out there.
When the other commenter mentioned doing lightweight scripts with PDO that's essentially what he meant though. Lightweight avoids reloading libraries and PHP is lightning fast when you do that.
A lot of progress has been made over the years to help PHP handle frameworks better, but there's a big reason why PHP grinds to a halt with heavy frameworks and that's it. Check out the techempower framework benchmarks.
Using PHP like Go, however, and just pulling in what you need can be extremely powerful.
Here's an entire presentation on it that I gave to a local PHP group. http://www.slideshare.net/barrywjones3/whats-the-right-php
FWIW, I do really like Laravel and even recommend it if you HAVE to use a big framework.