I've just run into this question asked in 2008. It has an accepted answer, which was good until 2009 when namespaces were introduced into PHP 5.3. But since 2010 it is no more correct, see my reaction.

It may not be the best example, but the point is:

What to do with obsolete posts that are no more correct?

They are usually inactive for months or years. Due to the time, the obsolete posts usually have many upvotes and only archaeologists bother to dig in them, but they have many views and the better the Google index them. In ten years, SO might be flooded with outdated, no-more-valid posts.

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    Add a comment to the accepted answer. If the author of the answer is still active, he can edit it to reflect the new info. If not, a 2K user can do that.
    – user000001
    Commented Jun 16, 2013 at 10:00
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    Exactly what you did is good, but I would probably leave out the big bold headline that say the accepted answer is obsolete. It's fine to mention it that the answer is outdated, but I don't see the need for a headline. Commented Jun 16, 2013 at 10:01
  • OK, but the answer hardly gains enough attention and if there is 30+ upvotes accepted obsolette answer, almost nobody would bother to scroll down to other answers. If other user edits the post, he shouldn't do any radical change. And the OP is very likely inactive after five years.
    – Jan Turoň
    Commented Jun 16, 2013 at 10:06
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    @JanTuroň that's why you also do what user000001 recommended and leave a comment on the obsolete answer. You can even link it to your own answer if you want. Commented Jun 16, 2013 at 10:10
  • @psubsee2003: OK, I did it. Let's see what will happen.
    – Jan Turoň
    Commented Jun 16, 2013 at 10:12
  • @JanTuroň not much is going to happen fast, it's not like those 31 upvotes showed up over night. But you did exactly what you can do to correct the answer. Commented Jun 16, 2013 at 10:14
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    @gnat I don't feel that is a duplicate. One asks for an automated mechanism and the other asks about what you can do as an user. Commented Jun 16, 2013 at 15:19
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    I think How to deal with obsolete answers? is definitely a duplicate; I agree that the other proposal doesn't really fit.
    – jscs
    Commented Jun 16, 2013 at 18:39

2 Answers 2


What to do with obsolete posts that are no more correct?

There is no one solution as it depends on situation and just how obsolete the answer is (is it outdated and just needs a minor edit to fine tune it or is it completely wrong and dangerous, or is it somewhere in between). How you proceed also depends on your comfort level with the topic and your own privileges (specifically if you have full-edit privileges or not).

If the post only needs a minor change

  • Leave a comment and explain the change and why
  • If the author of the answer is still active, hopefully the ping will get him/her to fix
  • If the author is no longer active or ignores the ping (after a few days), then go ahead and make the edit yourself.*
  • If the edit will completely change the answer (and not just add new info), then see the 2nd solution below.

If the post needs a significant change, is flat out is incorrect now, or the method is deprecated

  • Leave a comment and explain why the answer is no longer valid
  • Write your own answer, but it should be substantial, still answer the question, and still conform to the site's guidelines. Don't just post a link to a doc or off-site blog.
  • Editing in this case is not advisable as an edit would completely change the answer. Editing the obsolete answer just to add "This is obsolete" is also not appropriate. Basically just ignore the original answer aside from leaving a comment.

In either case, the community has decided that deletion is not a correct course of action, so deleting an outdated or obsolete answer is not going to happen. If you flag it, it will be declined.

A final option would be to retag the question with version specific tags. One thing you have to remember is obsolete doesn't always mean not useful to anyone. There are always people forced to use old version of languages and software and so an old solution might still have significant value. This option is not always viable for every situation, but if you have a case where retagging will not invalidate any answers, then it can help eliminate the confusion with out dated answers.

* - If you do not have full edit privileges, then it might be better to see if a 2K-er in chat or in meta can help as a suggested edit stands a good chance of getting rejected. But if you proceed with a suggested edit, make sure your comment is very descriptive

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    Oh, deleting would be too harsh: even obsolete invalid information can be useful to those dealing with legacy issues. Maybe vote to mark as obsolete feature might be added, so in the future the posts could be handled somehow?
    – Jan Turoň
    Commented Jun 16, 2013 at 10:53
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    @JanTuroň Agreed on both points. I tried to write the answer to be as general as possible, and deletion is something I've seen asked about for obsolete answers. Actually instead of an obsolete flag, I think answer-specific tags for specific versions might be appropriate because obsolete is never really obsolete, it is still valid for people using older versions Commented Jun 16, 2013 at 11:01
  • Good idea: I tagged the question as php-5.3 - I believe the problem is solved.
    – Jan Turoň
    Commented Jun 16, 2013 at 11:20
  • The feature as suggested by @JanTuroň can be added so that it will help a lot in understanding the obsolete posts and will also help in cleanup of such posts. <br/> The obsolete posts may be of any help to someone dealing with legacy systems. So, deleting will not completely solve the problem I guess. Commented Jun 16, 2013 at 11:55
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    Well, in the second case (flat-out obsolete), an edit would still be helpful. Instead of "this is obsolete" (which sounds rather harsh and not very informational), you could put a note like "This only applies to version 5.12 and earlier". Commented Jun 16, 2013 at 12:29
  • @doubleDown: Can you put that up as an answer? I think it clarifies that the answer is only applicable for certain version. The comments should only serve to inform the author, rather than the readers.
    – nhahtdh
    Commented Jun 16, 2013 at 13:17
  • @nhahtdh, I guess so I could put it as an answer. Commented Jun 16, 2013 at 15:16

In my opinion, if a post is "obsolete" (i.e. the issue it addresses does not exist anymore or there are better ways to do it in more recent versions), the best thing to do is to edit the post to put a note along the lines of "This only applies to version 5.12 and earlier". This is more informative and less harsher than editing it to say "This is obsolete".

The post may be obsolete in the more recent versions of the program/language, but it might still be the perfect solution for those using older versions. Sometimes, an updated answer might not even work at all with the older versions because it uses some newer features that does not exist in older versions.

In any case though, do post an up-to-date answer, and also include the fact that this new answer only works for certain versions and above.

  • +1 because I frequently work with legacy code, and often need these "obsolete" answers. Not everyone can work with only the latest and greatest technologies, and having something that specifically mentions the version # is extremely helpful to me :)
    – Rachel
    Commented Jun 16, 2013 at 15:45

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