Installing Drupal

 Step 3 of 11.8 says: 

Copy all of the files from the web root of your live site to the web root of your development site.

If a site is created using 

There is already a docs page about this:
https://www.drupal.org/docs/testing/phpunit-in-drupal/running-phpunit-tests

I've tried to follow that, including creating a browser_output directory and setting up the configuration file (phpunit.xml).

But #2 in the instructions is a stumbling block. It says:

Should my git repo be in my_project_dir or my_project_dir/web?

I have been working with Drupal for a few months, but I am just beginning to get familiar with composer on my localhost. I have completed an install.

When I proceed to my-project/web/core/install.php I receive the message, 'Your PHP installation is too old. Drupal requires at least PHP 7.3.0. See the system requirements page for more information.'

When I check the php version on my machine, I find:

If I run composer require drush/drush on a brand new out-of-the box D8.8 or D9.0 site (on shared hosting), then it will mostly FAIL with less than PHP memory_limit = 2768Mb (always fail with less than 1 GB).