Fixed usage of imported namespace.

The use statement imports \ArrayObject as PhpArrayObject so we need to use it here. In other case it will use of undefined constant.
Merging #5322
Merge branch 'lucascorbeaux-hotfix/5232'

* lucascorbeaux-hotfix/5232:
  Added a few comments to the test, change var name
  Fixing a bug that causes fatal error when a RowGateway's primary key were changed directly : refresh the select's where clause after the update query.
Merge pull request #5507
Merge pull request #5507 in develop