Debug mode requires two small file edits in vBulletin 5. This is because VB5 has two config.php files by design. Both files require an edit and it is a little different for each.
Please note- before editing any PHP files be sure you have a real code/text editor. The built in Windows Notepad should never be used to edit PHP files- Windows Notepad can often add invisible characters to code files that will cause errors once your re-upload the edited files. Windows users should instead download one of the many free alternatives. Two popular free text editors for Windows (all versions) are:
Notepad2 - Available from Flo's Freeware - Looks almost exactly like regular Notepad, Native 32bit and 64bit versions.
Notepad++ - Available from notepad-plus-plus.org - A little more advanced than Notepad2
I am not aware of any problems with the built in text editors in Max OSX or Linux but there are plenty of advanced free editors available for all systems.
Once you have your text editor setup the first edit is to your front-end or "Presentation" config,php file. This is the one in your forum-root directory.
Download this file from your server and open it in a text editor. Look for the line that says:
$config['debug'] = false;
Here is a screenshot from the VB 5.0.5 config.php file-
Edit the line to say:
$config['debug'] = true;
Test your site- make sure it loads- it should- if you run into any problem simply re-copy the original config.php file from the original VB Install package and overwrite it, but it is very unlikely you will have an issue.
Now we must make the 2nd edit. This edit is to the back-end or "core" config.php file which is in your /core/includes/ directory.
This file contains a lot of important information for your database which is not as easily replaced as the front-end file should something go wrong, so please save a back-up of this file somewhere else on your computer before editing the original file.
Download a copy of this file and find the line that says
// $config['Misc']['debug'] = true;
Edit the line to remove the two slashes // at the front and then re-save and re-upload the file.
$config['Misc']['debug'] = true;
You will know it is in debug mode when there is a bunch of extra information shown below pages on the front end- example:
Debug mode in the back-end (Admin CP) is a little less noticeable. There will be several new/more options mostly for those developing their own modifications. One way to tell is to go to Admin CP -> Style Manager and you will now see the "Master Style" visible above all other styles as below:
If you see these changes you have confirmed you are in debug mode.
To disable debug mode you basically reverse the above, edit each file and undo the changes.
Note- if in either of the above files you can't find the text I say to look for you can safely simply add the line $config['debug'] = true; to the front-end/presentation file or $config['Misc']['debug'] = true; to the back-end/core file and that will work as well. Add it at the very top, just below the first line of the file which should be <?php.
To undo the above changes simply comment out the line by adding two slashes // at the start of the line so it will be ignored as if it didn't exist. This way should you need to enable it again you just have to remove those slashes.