Dokuwiki - Error internal 500 on php
About
When upgrading a dokuwiki installation, you may get a 500 internal server error page.
Solution / Possible cause
This is caused mostly by a syntax error somewhere in the code of a plugin.
Solving the errors
From the command line, you can check that with the below command:
cd dokuwiki
php -d error_reporting=-1 -d display_errors=On doku.php
Example of output:
Fatal error: Declaration of action_plugin_tag::register(&$contr) must be compatible
with dokuwiki\Extension\ActionPlugin::register(Doku_Event_Handler $controller)
in /opt/www/lib/plugins/tag/action.php on line 22
This output shows that this is the tag plugin that causes the problem. You can disable it easily if you rename the folder.
mv lib/plugins/tag lib/plugins/tag.bad
Plugin that I have disabled:
Solving the warning
From the command line, you can check that with the below command:
cd dokuwiki
php -d error_reporting=32767 -d display_errors=On doku.php | grep -i warning
Example of output:
Warning: Use of undefined constant DOKU_LEXER_EXIT - assumed 'DOKU_LEXER_EXIT'
(this will throw an Error in a future version of PHP) in /opt/www/lib/plugins/webcomponent/syntax/cardcolumns.php on line 155