Comment 2 for bug 1882279

Hi Dustin and thanks for this bug report. Benchmarking is difficult and repeating one single operation several time is often not a good performance indicator, however I agree we shouldn't see such a huge difference. I can reproduce it too as follows:

1. Launch a Focal LXD container
2. apt install php
3. Run `php test.php` (your test script, unmodified). On my machine this it runs in about 1.5s.

Now in docker:

4. mkdir php-perf-test, copy test.php in this directory and create a Dockerfile containing the following:

FROM php:7.4-cli
COPY . /tmp/php
WORKDIR /tmp/php
CMD [ "php", "./test.php" ]

5. Run: `docker build -t my-php-app .`
6. Run: `docker run -it --rm --name my-running-app my-php-app`. The test script runs in about 0.25 in this case, on the same machine.

Version info for the Ubuntu packaged PHP:

$ apt policy php7.4
php7.4:
  Installed: 7.4.3-4ubuntu2.2

$ php --version
PHP 7.4.3 (cli) (built: May 26 2020 12:24:22) ( NTS )
Copyright (c) The PHP Group
Zend Engine v3.4.0, Copyright (c) Zend Technologies
    with Zend OPcache v7.4.3, Copyright (c), by Zend Technologies

while the Docker version is:

$ docker run -it --rm --name my-running-app my-php-app php --version
PHP 7.4.6 (cli) (built: May 15 2020 12:47:30) ( NTS )
Copyright (c) The PHP Group
Zend Engine v3.4.0, Copyright (c) Zend Technologies

This is worth some more investigation.