DokuWiki has debugging tools. Some need to be configured.

When config option allowdebug is enabled you can:

• Appending ?do=debug or &do=debug to URL so DokuWiki will output a huge list of debug strings.
• Look up output of dbglog() in data/cache/debug.log
• Receive additional error messages e.g. from some authentication backends

Appending ?do=check or &do=check to URL triggers the action mode check that provides some information about the users permissions and the DokuWiki setup.

See the debug info at the indexer page.

• dbg($msg)
  Insert a code block in the wikipage filled by $msg as plain text.
  
  Adding an extra argument to dbg($msg, $hidden=true) will return the $msg as html comment.

• dbglog($msg)
  Writes $msg to the log in the cache directory data/cache/debug.log when the config allowdebug is enabled. Be aware the log isn't emptied automatically.
  
  Use dbglog($msg, 'Header above log message') for including a header above $msg.

• dbg_deprecated($alternative = '')
  Function to mark deprecated functions. Each call is logged to the debuglog, when the config allowdebug is enabled. The log message mentions: the name of the deprecated function, the function using it, its file and line and the $alternative when provided.

• dbg_backtrace()
  Print a reversed, prettyprinted backtrace

• debug_guard($data)
  When you write your own debug functionality, use this function to remove all data from an array where the key seems to point to sensitive data.

• Configuration option allowdebug
• Caching