Description:
------------
I used the function preg_match_all () WITHIN a function being called by another function, with a named capturing group and assigned the match to a variable using the named group as a key (name or number).

The variable assigned the value of the return becomes NULL

This happens in both the latest snapshots of PHP-4 and PHP-5 with PHP-5 giving a segmentation fault after NULL when "error_reporting (E_ALL)" is at the top of the script

When the configure option --enable-debug is used PHP-5 gives UNKNOWN:0 instead of NULL and no segmentation fault

When NOT using a Named capturing group name and instead use a normal capturing group the behaviour seems to stop. Assigning the matched value by reference also seems to stop the behaviour. ie var2=&var['named_key']

Reproduce code:
---------------
error_reporting(E_ALL);
function func1(){
        $words = func2();
        var_dump($words);
        $this_words = $words;
        return $this_words;
}
function func2(){
        $pattern = '(?P<word>(?:the))';
        $string = 'what the word and the other word the';
        preg_match_all('/'.$pattern.'/i', $string, $matches);
        $words = $matches['word'];
        $this_words = $words;
        var_dump($this_words);
        return $words;
}
func1();

Expected result:
----------------
array(4) {
  [0]=>
  string(3) "the"
  [1]=>
  string(3) "the"
  [2]=>
  string(3) "the"
  [3]=>
  string(3) "the"
}
array(4) {
  [0]=>
  string(3) "the"
  [1]=>
  string(3) "the"
  [2]=>
  string(3) "the"
  [3]=>
  string(3) "the"
}


Actual result:
--------------
array(4) {
  [0]=>
  string(3) "the"
  [1]=>
  string(3) "the"
  [2]=>
  string(3) "the"
  [3]=>
  string(3) "the"
}
NULL{php -4} UNKNOWN:0 {php-5 --enable-debug}
segmentation fault {php-5 without --enable-debug}

Backtrace (PHP-5 latest without enable-debug because it doesn't crash when it is used)
---------------------------------------
(gdb) bt
#0  0x402429f2 in malloc () from /lib/i686/libc.so.6
Cannot access memory at address 0x18
(gdb)