[pmwiki-devel] Cannot Save Larger Pages

[Petko Yotov]

For PmWiki 2.6.1, I added a function to check if the temp directory is 
readable. If not, a message should appear above the edit form, above the 
upload form, and in the ?action=diag output.

This is a tricky bug, however unlikely, because the only apparent reason 
is the page length, adding a few characters may go over the internal PHP 
buffer which is 8 or 16 kB, and this prevents the post to reach PmWiki.

Petko

-- 
If you upgrade :  https://www.pmwiki.org/Upgrades

On 11/06/2026 16:32, Petko Yotov wrote:
> Great, I'll add this to Troubleshooting.
> 
> Petko
> 
> On 11/06/2026 15:50, Michael Elliott wrote:
>> Its fixed!
>> 
>> Ending up being a Hosting company issue.  Below is that they said they
>> changed to fix in case anyone else comes across this:
>> 
>>> During testing, we were able to reproduce behavior consistent with
>>> the PHP warnings you previously reported.
>>> The issue we found was that PHP was unable to create temporary files
>>> in the configured temporary directory (D:\PHP\temp). This was
>>> consistent with the warnings regarding temporary file creation and
>>> POST data buffering.
>>> 
>>> To address this, we updated the permissions on the PHP temporary
>>> directory and confirmed that PHP can now successfully create
>>> temporary files.
>>> After making this change, we performed additional testing using a
>>> standalone PHP form and successfully processed POST requests larger
>>> than 20 KB. This exceeds the approximately 14 KB threshold where you
>>> reported the PMWiki save failures occurring.
>>> 
>>> Based on our testing, the issue does not appear to be related to the
>>> configured PHP POST size limit or IIS request size limits.
>> 
>>  On Thursday, June 11, 2026 at 09:18:37 AM EDT, Michael Elliott
>> <melliott42 at yahoo.com> wrote:
>> 
>> Petko, Team,
>> 
>> Thank you for the quick response.  I am working through all the
>> options you presented.
>> 
>> Also, the troubleshooting page is really good.  I just never needed it
>> before using PMwiki for many years. Shows how solid its been.
>> 
>> The Troubleshooting item below seemed to have my name on it but in
>> initially creating a new page the issue still exists:
>> 
>>> Very long pages with thousands of lines may appear blank after
>>> adding a few additional lines. This may be preformatted text, table,
>>> or text inside conditional markup, or text in a custom markup
>>> directive.
>>> @ini_set('pcre.backtrack_limit', 10000000);
>>> 
>>> Testing this further...
>> 
>> I'll add that on some saves of pages with more data I sometimes get
>> this (below) which would suggest it is in the PHP config:
>> 
>>> PHP Notice: Unknown: file created in the system's temporary
>>> directory in Unknown on line 0
>>> 
>>> PHP Warning:  Unknown: Unable to create temporary file, Check
>>> permissions in temporary files directory. in Unknown on line 0
>>> PHP Warning:  Unknown: POST data can't be buffered; all data
>>> discarded in Unknown on line 0
>> 
>> Thank you,
>> 
>> Michael
>> 
>>  On Thursday, June 11, 2026 at 07:18:54 AM EDT, Petko Yotov
>> <5ko at 5ko.fr> wrote:
>> 
>> If this is a bug with the PmWiki core we'll fix it ASAP.
>> 
>> I just saved a 350kb page on pmwiki.org and the same one on my laptop
>> 
>> wiki, both running the pre-release after version 2.6.0.
>> 
>> What messages appear on the wiki or in the server's PHP error logs? A
>> 
>> 500 error almost certainly contains some indication in the error logs.
>> 
>> Do you see a blank 500 Internal Server Error page, or does the edit
>> form
>> 
>> reappear unsaved, or does it redirect to the page that was not
>> modified?
>> 
>> If you press Preview, does the preview page work?
>> 
>> Can you upload files larger than 14kb via the wiki?
>> 
>> Do you have mod_security enabled, or something similar that may block
>> 
>> the request for specific security-related keywords in the posted text?
>> 
>> Do you have enough disk space?
>> 
>> Can you save smaller pages, subsequently?
>> 
>> Can you create new pages that are larger? Can you delete pages? Can
>> you
>> 
>> delete larger pages?
>> 
>> Is the problem with the full disk file size
>> 
>> (pmwiki/wiki.d/Main.HomePage) or with the size of the wiki markup text
>> 
>> 
>> in the edit form?
>> 
>> Do you use any custom page store class?
>> 
>> Does this happen in one wikigroup, or in all wikigroups?
>> 
>> Can you save a small page but not a large one in the same wikigroup?
>> 
>> Check directory/file permissions under wiki.d/.
>> 
>> Do you have recipes that are only enabled on ?action=edit or that
>> modify
>> 
>> $EditFunctions?
>> 
>> Does this happen in an empty PmWiki installation? If so, the problem
>> may
>> 
>> be with the server configuration, otherwise it is more likely with a
>> 
>> local PmWiki customization. See Troubleshooting on how to track what
>> is
>> 
>> causing this.
>> 
>>   https://pmwiki.org/Troubleshooting
>> 
>> Petko
>> 
>> On 11/06/2026 12:40, Michael Elliott wrote:
>> 
>>> Hello,
>> 
>>> 
>> 
>>> I started having an issue where saving pages where the data size is
>> 
>>> larger than ~14.5 fail.  I have multiple PMwiki instances and it is
>> 
>>> happening on all of them.  Upgrading to the latest PMwiki version
>> had
>> 
>>> no effect.  I also purge all page history and also tried recreating
>> 
>>> the page using a new name with no effect.
>> 
>>> 
>> 
>>> I have been working intensely with my hosting company and they say
>> 
>>> there should be no issue (below).
>> 
>>> 
>> 
>>> We checked the standard server-side request size limits. PHP is
>> 
>>> currently allowing POST requests up to 24 MB, and IIS request
>> 
>>> filtering is allowing up to approximately 28.6 MB. A 14 KB save is
>> far
>> 
>>> below both of those limits, so this does not appear to be caused by
>> 
>>> the normal PHP POST size limit or IIS request-size limit.
>> 
>>> 
>> 
>>> We are continuing to review this from the IIS/FastCGI side and will
>> 
>>> check for any related server-side errors or rules that may be
>> 
>>> triggering the 500 error during the PMWiki save request.
>> 
>>> 
>> 
>>> What can you recommend?
>> 
>>> 
>> 
>>> Thank you,
>> 
>>> 
>> 
>>> Michael Elliott