Re: foreach weirdness

On Sun, Mar 25, 2012 at 4:11 PM, Arno Kuhl <arno@dotcontent.net> wrote: > From: Simon Schick [mailto:simonsimcity@googlemail.com] > Sent: 24 March 2012 12:30 AM > To: Robert Cummings > Cc: arno@dotcontent.net; php-general@lists.php.net > Subject: Re: [PHP] foreach weirdness > > 2012/3/23 Robert Cummings <robert@interjinn.com> >> >> On 12-03-23 11:16 AM, Arno Kuhl wrote: >>> >>> >>> it still does not produce the correct result: >>> 0 1 3 6 10 15 21 >>> 0 1 3 6 10 15 15 >> >> >> This looks like a bug... the last row should be the same. What version >> of PHP are you using? Have you checked the online bug reports? >> >> > > Hi, Robert > > Does not seem like a bug to me ... > > http://schlueters.de/blog/archives/141-References-and-foreach.html > > What you should do to get the expected result: > Unset the variable after you don't need this reference any longer. > > Bye > Simon > > -- > > Hi Simon, unsetting the $value does fix the problem, but I found that any time you assign > $value by reference in a foreach loop you have to do an unset to avoid corrupting the array unless > you continue to assign $value by reference (as illustrated in the article you linked). > > So doing something as simple as: > $array = array(0, 1, 2, 3, 4, 5, 6); > foreach ($array as $key=>&$value) { >        echo "Key: $key; Value: $value<br />\n"; > } > > and then follow with (from the php manual): > foreach ($array as $key=>$value) { >        echo "Key: $key; Value: $value<br />\n"; > } > > will not only give the wrong result, it will corrupt the array for *any* further use of that > array. I still think it’s a bug according to the definition of foreach in the php manual. Maybe > php needs to do an implicit unset at the closing brace of the foreach where was an assign $value by > reference, to remove the reference to the last element (or whatever element it was pointing to if > there was a break) so that it doesn't corrupt the array, because any assign to $value after the > foreach loop is completed will corrupt the array (confirmed by testing). The average user (like me) > wouldn't think twice about reusing $value after ending the foreach loop, not realising that > without an unset the array will be corrupted. > > BTW thanks for that reference, it was quite an eye-opener on the pitfalls of using assign by > reference, not only in the foreach loop. > > Cheers > Arno Note that somewhat similar error was discussed on this list a few months ago[1]. You could probably have solved it yourself if you searched the mailing list archives. - Matijn [1] http://www.mail-archive.com/php-general@lists.php.net/msg269552.html