Description:
------------
array_walk_recursive contains code to detect recursion in arrays where the recursion depth is 1. But deeper recursion is not detected, leading to the code recursing until the stack depth becomes too great and a crash occurs.

It seems clear from the code that the problem is in php_array_walk in ext/standard/array.c. The following test only detects single level recursion:

                        if (thash == target_hash) {
                               php_error_docref(NULL TSRMLS_CC, E_WARNING, "recursion detected");
                                 return 0;
                         }

Reproduce code:
---------------
<?php
function myfunc($value,$key) { echo "value: $value, key: $key \n";}
$a=array(array(),"foo"=>"bar");
$a[0][]=&$a;
array_walk_recursive($a,"myfunc");
echo "reached end \n";
?>

Expected result:
----------------
value: bar, key: foo
reached end

Actual result:
--------------
Segmentation fault