Description:
------------
We're working on making Drupal 8 compatible with PHP7.

A few of our tests are failing with very strange array related errors.

A lot of test that have a common base class and call the same method are failing with the same problem. See https://www.drupal.org/node/2454439#comment-9788325.

Basically, there are two arrays, both are keyed with the same keys. We loop over one of them and access the element in the second array. That results in a undefined index notice. But when comparing with array_keys() or var_dump(), then the array key exists.

Changing the code to instead do a foreach and look for the matching key works fine:

-      $migration = $migrations[$migration_id];
+      foreach ($migrations as $id => $migration) {
+        // WTF PHP7, you drunk?
+        if ($id === $migration_id) {
+          break;
+        }
+      }

@ircmaxell has been debugging this and tracked it down to a hash collision between the array entries d6_user and d6_node_type, which then results in d6_node_type not being accessible. For other tests, it's other keys.

This only happens in this specific scenario, we haven't been able to reproduce it in a standalone script.

To run the test, get the latest Drupal 8 (branch 8.0.x), and run the test like this:

php7 core/scripts/run-tests.sh --sqlite /tmp/test.sqlite --dburl sqlite://tmp/db.sqlite --class "Drupal\migrate_drupal\Tests\d6\MigrateCckFieldRevisionTest"

Notes: that needs the curl and gd extensions, and it starts a second script to actually run the test. To debug with gdb for example, you need something like this:

gdb --args '/usr/local/bin/php7' './core/scripts/run-tests.sh' --url '' --sqlite '/tmp/test.sqlite' --dburl 'sqlite://tmp/db.sqlite' --php '/usr/local/bin/php7' --test-id 1 --execute-test 'Drupal\migrate_drupal\Tests\d6\MigrateCckFieldRevisionTest'

(the first command needs to be run first, to set up the env, look for proc_open and print the command to get he right now)