Hi Nikita,
Before talking about solutions, can the people who need this first outline > what functionality is needed and what it is needed for (and maybe what > workarounds you currently use). E.g. do you only need to know whether > something is a reference, or do you need to know whether two somethings are > part of the same reference, etc. There are probably multiple use cases for > this with different needs. > We're using reference introspection to do both: we need to know when a zval is a reference, and we also need to track each of them separately. The use case is being able to intropect any arbitrary PHP datastructure, with one main application: providing an enhanced "dump()" function. See e.g. this screenshot for what we get using the dump() function provided by Symfony VarDumper component: https://symfony.com/doc/current/_images/07-hard-ref.png In PHP5 days, Julien Pauli wrote a PHP extension to do zval introspection. Here is the code + README (see test case 001.phpt for example with references.): https://github.com/symfony/symfony/tree/3.4/src/Symfony/Component/Debug/Resources/ext With PHP7, using pure PHP introspection is easier to maintain and still very fast so we deprecated the extension. Here is the code doing reference introspection: https://github.com/symfony/symfony/blob/master/src/Symfony/Component/VarDumper/Cloner/VarCloner.php#L83 it might not be easy to follow, but the basic blocks are: $array2 = $array1; $array2[$key] = $unique_cookie; if ($array1[$key] === $unique_cookie) => we found a reference then we also maintain a registry of $unique_cookie so that we know if we already saw that reference or not (the check is done before the above "if" or course.) Cheers, Nicolas
