Pmwiki is pretty robust and can automatically adapt to a very wide variety of environments. However, sometimes things don't go as we expect, so we're catalogging common errors and their fixes here.

Troubleshooting Frequently Asked Questions

Note: This page on is probably not the best place to post questions. Consider sending questions to the pmwiki-users mailing list, or post your question on the PmWiki:Questions page.

Why am I seeing strange errors after upgrading?

Make sure all of the files were updated, in particular pmwiki.php. Sometimes an FTP or other copy program will fail to transfer all of the files properly.

If you renamed pmwiki.php to index.php, then upgrading won't have updated your index.php file, and you now know why the installation notes advise against doing this.

Lastly, be sure all of the files in the wikilib.d/ directory were also upgraded. Sometimes it's a good idea to simply delete the wikilib.d/ directory before upgrading (local copies of pages are stored in wiki.d/ and not wikilib.d/).

I'm suddenly getting messages like "Warning: fopen(wiki.d/.flock): failed to open stream: Permission denied..." and Cannot acquire lockfile"... what's wrong?

Something (or someone) has changed the permissions on the wiki.d/.flock file or the wiki.d/ directory such that the webserver is no longer able to write the lockfile. The normal solution is to simply delete the .flock file from the wiki.d/ directory -- PmWiki will then create a new one. Also be sure to check the permissions on the wiki.d/ directory itself.

My links in the sidebar seem to be pointing to non-existent pages, even though I know I created the pages. Where are the pages?

Links in the sidebar normally need to be qualified by a WikiGroup in order to work properly. Otherwise they will point to whatever group you happen to be viewing the sidebar in.

Why am I seeing "Warning: Cannot modify header information - headers already sent ..." messages at the top of my page.

If this is the first or only error message you're seeing, it's usually an indication that there are blank lines or spaces before the <?php or after the ?> in a local customization file. Double-check the file and make sure there aren't any blank lines or spaces before the initial <?php. It's often easiest and safest to eliminate any closing ?> altogether.

If the warning is appearing after some other warning or error message, then resolve the other error and this warning may go away.

Why is PmWiki prompting me multiple times for a password I've already entered?

Usually this is an indication that the browser isn't accepting cookies, or that PHP's session handling functions on the server aren't properly configured. If the browser is accepting cookies, then try setting $EnableDiag=1; in local/config.php, run PmWiki using ?action=phpinfo, and verify that sessions are enabled and that the session.save_path has a reasonable value. Note that several versions of PHP under Windows require that a session_save_path be explicitly set (this can be done in the local/config.php file).

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