reused hash tables in large data structures in PHP7

Hi, I've encountered a hard-to-consistently-reproduce issue with HashTable zvals. I have code that will generate big nested \stdClass structures for JSON encoding. It does so using classes that have methods that generate those fields. For example, you could have a class like this: class Block { public function css_classes() { return ['x', 'y', 'z']; } } Other code would translate it into a value that would var_dump() as this: object(stdClass)#1 (1) { ["css_classes"]=> array(3) { [0]=> string(1) "x" [1]=> string(1) "y" [2]=> string(1) "z" } } The template data could include multiple instances of Block. As in, a \stdClass could be generated with multiple copies of that array content. That data could get sent to json_encode(), which uses ZEND_HASH_APPLY_PROTECTION/etc. to avoid recursion. I've seen situations where that array of strings triggers that recursion check. But it's not always, and a php-fpm restart can make it go away. Can anyone think of why this might happen? Thanks, Adam