#21702 [Opn]: nested foreach on same array using reference fails
| From: | moriyoshi@php.net | Date: | Fri, 17 Jan 2003 08:23:32 +0000 |
| Subject: | #21702 [Opn]: nested foreach on same array using reference fails | ||
| References: | 1 | Groups: | php.doc |
| Request: | Send a blank email to phpdoc+get-969350961@lists.php.net to get a copy of this message | ||
ID: 21702
Updated by: moriyoshi@php.net
Reported By: vdvo@vdvo.net
Status: Open
-Bug Type: Scripting Engine problem
+Bug Type: Documentation problem
-Operating System: Linux (but probably any)
+Operating System: Any
-PHP Version: 4.2.2
+PHP Version: Any
New Comment:
Actually this is a dupe of bug #14607, but this PR is much more
concise than that, so I'm going to keep 14607 bogus and make this
alive.
Since foreach() uses "internal array pointer" and references are
designed
to share one such pointer, the deeper loop gets confused and your
script never
gives the expected result.
Virtually the script can be rewritten as...
<?php
$a = array(1, 2);
for ($ptr = 0; $ptr < count($a); $ptr++) {
$b = $a[$ptr];
echo "outer: $b <br />\n";
for ($ptr = 0; $ptr < count($a); $ptr++) {
$c = $a[$ptr];
echo "inner: $c <br />\n";
}
}
?>
Marking this as a documentation problem.
Previous Comments:
------------------------------------------------------------------------
[2003-01-16 20:05:14] vdvo@vdvo.net
Try this:
<?php
$a = array(1, 2);
$ref =& $a;
foreach ($ref as $b) {
echo "outer: $b<br>\n";
foreach ($a as $c)
echo "-- inner: $c<br>\n";
}
?>
The output is:
outer: 1
-- inner: 1
-- inner: 2
(i.e., the processing stops after the first iteration of the outer
foreach). If I understand the docs well, the output should be:
outer: 1
-- inner: 1
-- inner: 2
outer: 2
-- inner: 1
-- inner: 2
When you remove the ampersand from the assignment to $ref, it works as
expected.
The documentation is a bit unclear on this. It says "Also note that
foreach operates on a copy of the specified array, not the array
itself, therefore the array pointer is not modified as with the each()
construct...", which leads me to believe that the sample code should
work. But then it goes on to say: "However, the internal pointer of the
original array *is* advanced with the processing of the array.", which
seems to contradict the first quotation???
This is probably a dupe of bug #14607, but that one is closed as
"bogus" and I can't reopen it. Also see bug #5052, which is similar but
not quite, and it's closed.
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/?id=21702&edit=1