Fix serialize() throwing for arrays that refer to themselves through references of refcount 1 - #24446

References of refcount 1 are dereferenced by serialize() and never recorded in the variable table, so an array that contains itself through such references recurses until the stack limit and throws an Error. Protect against recursion only for the arrays reached through such a reference, so that arrays shared by several objects are still written in full.

To reproduce

<?php
function mk() { $p = ["n" => "p"]; $c = ["n" => "c"]; $c["parent"] = &$p; $p["children"][] = &$c; return $p; }
echo strlen(serialize(mk())), "\n";

php repro.php on PHP 8.5.4

Before: Error: Maximum call stack size of 8339456 bytes (zend.max_allowed_stack_size - zend.reserved_stack_size) reached. Infinite recursion?

After: 131