Site crashed after installing

Hi Carlos,

Thank you for your message.

To better understand the issue, could you please share more details?

• Which specific page or action triggers the crash?
• Does it happen in the frontend, backend, or both?

Please also enable Joomla Debug and Error Reporting → Maximum so you can get the full stack trace. This will help identify exactly where the array_merge(): Argument #1 must be of type array; null is provided error is coming from.

Once you have the detailed error message, please paste it here and I’ll help you resolve it right away.

Kind regards,
Lefteris

Hi Carlos,

Thank you for the update.

I just tested CommentBox 1.2.0 on a clean Joomla 5.4.0 installation and couldn’t reproduce the issue, so it seems that something in the environment is returning a null value where Joomla normally provides an array. CommentBox expects an array in that part of the code, and another plugin modifying the content pipeline can cause this.

We will add a safety check in the next CommentBox release to prevent this error from appearing even when another extension returns invalid data. However, the underlying cause is most likely a third-party plugin that isn’t fully compatible with Joomla 5.4.

To identify the source, please try the following:

1. Update all third-party extensions to their latest versions to ensure Joomla 5.4 compatibility.
2. If the problem persists, disable content-related plugins one by one (especially “Content”-type plugins) and test the frontend after each change. This will help locate the plugin returning a null value.
3. Once we know which plugin is causing it, I can advise you further or provide a workaround. 

Let me know which plugin is responsible once you locate it, and I’ll be happy to help you resolve it.

Kind regards,
Lefteris

Hi Carlos,

Thank you for the detailed follow-up — that information is really helpful.

Based on everything you’ve tried, I agree that this is very likely caused by stale data or behavior left over from an older Joomla / extension setup. In Joomla 5.4, the onContentBeforeDisplay event is expected to return an array, but in your case it’s coming back as null, which causes array_merge() to fail.

Temporary workaround (safe to apply)

You can safely fix this by adjusting one line in CommentBox so it defensively casts the value to an array.

Please edit the following file:

plugins/content/commentbox/src/Extension/CommentBox.php

At line 182, replace the existing line with this:

$event->setArgument('result', array_merge((array) $event->getArgument('result'), [$html]));

This ensures that even if another plugin (or legacy data) returns null, CommentBox will continue to work correctly.

Permanent fix

I will include this safeguard in the next CommentBox release, so no manual change will be needed going forward.

After applying the change:

• Clear Joomla and browser caches
• Reload the frontend

Please let me know if this resolves the issue on both sites.

Thank you again for your patience and for the thorough debugging — I really appreciate it.

Kind regards,
Lefteris

Hi Carlos,

That’s excellent to hear — I’m really glad it worked on both sites!

Thank you very much for your kind words and for taking the time to leave a rating on the JED. It’s truly appreciated and helps a lot in supporting and improving the extension.

If you have any questions in the future or need assistance with CommentBox, feel free to get in touch anytime.

Best regards,
Lefteris