Can be very useful for big projects, when you create a lot of objects that should stay in memory. So GC can't clean them up and just wasting CPU time.
Issue in composer:
https://github.com/composer/composer/pull/3482#issuecomment-65199153
Solution and people replies:
https://github.com/composer/composer/commit/ac676f47f7bbc619678a29deae097b6b0710b799