Does Drush 8.x work with core 7.x?

Question

With the major changes to Drupal with version 8, it seems I would need Drush 7.x or earlier to work with Drupal 7.x. I tried to rebuild the cache and I got errors related to namespaces in PHP. It seemed to be looking for features that were not part of Drupal 7.x.

Are there different commands to clear the cache for a Drupal 7.x site?
I tried drush cr and it came back with errors indicating it was trying to find code using namespaces, but Drupal 7.x core doesn't use namespaces in the code.

I tried it on Ubuntu and on Windows.

Answer 1

Yes, Drush 8 works with Drupal 6, 7 and -8.3. I just tested Drush 8.1.17 against a Drupal 7.58 site: worked a charm to clear cache, generate a login URL and download a module.

This is the compatibility table from their site for reference:

I mean are there different commands to clear the cache for a Drupal 7.x site?

Yes, it was cache-clear, or cc for short in Drupal 7, e.g.

drush cc all

Answer 2

The current way of installing Drush is to add the version you need on a per-project basis, using composer require drush/drush. Then you install Drush Launcher, which will use the drush in the directory of whatever site you are working on.

Answer 3

It's better to use the both of drush with different aliases, for example use drush8 for drush core 8.x and drush7 for drush core 7.x. To do that install the both drush version and use two symbolic links (for Mac):

ln -sv path_to_drush7_installation_folder/drush /usr/local/bin/drush7
ln -sv path_to_drush8_installation_folder/drush /usr/local/bin/drush8

And then to clear cache for example you can use :

• For a Druapl 8 project:

  drush8 cr

• for a Drupal 7 project:

  drush7 cc all