Fatal Error: Undefined T4PATH_ Constants*

4creator

Hello,

I’m not a PHP developer, so I asked an AI assistant to help me draft this report in a clear and structured way.
The following is an AI-assisted summary of the issue and the relevant findings.

Summary
On a Joomla site using the T4 System Plugin + t4_bs5_blank template, the frontend fails with multiple PHP fatal errors such as:
• Undefined constant "T4\Helper\T4PATH_BASE"
• Undefined constant "T4\Helper\T4PATH_LOCAL"
• Undefined constant "T4\Document\T4PATH_BASE_URI"

Switching the site template to Cassiopeia avoids the error, so this appears to be specific to T4.

Environment
• Joomla: 5.4.2
• PHP: 8.2.20
• T4 System Plugin: 2.5.4
• Template: t4_bs5_blank: 1.3.0
• Other relevant extensions: Regular Labs System Plugin is enabled (seen in stack trace), but the crash happens inside T4 code before output.

What happens (Actual behavior)
The site throws a fatal error and stops rendering. Example stack traces:
1) Undefined constant T4PATH_BASE

Exception Type: Error
File: /plugins/system/t4/src/t4/Helper/Asset.php
Message: Undefined constant "T4\Helper\T4PATH_BASE"

2) Undefined constant T4PATH_LOCAL

Exception Type: Error
File: /plugins/system/t4/src/t4/Helper/Path.php
Message: Undefined constant "T4\Helper\T4PATH_LOCAL"

3) Undefined constant T4PATH_BASE_URI

Exception Type: Error
File: /plugins/system/t4/src/t4/Document/Template.php
Line: 203
Message: Undefined constant "T4\Document\T4PATH_BASE_URI"

In Template.php, the fatal is triggered by this line inside renderHead():

$this->doc->addScript(T4PATH_BASE_URI . '/js/base.js', ['version' => 'auto']);

Technical analysis (why this looks like a T4 bug)
From the errors and the namespace-qualified constant names shown in the messages (e.g., T4\Document\T4PATH_BASE_URI), PHP is treating these as constants that are referenced before they are defined.

This suggests either:
1. The constants are not defined at all in this execution path, or
2. The constants are defined somewhere in T4, but initialization order / load order causes them to be referenced too early.

Because multiple files fail in the same way (Asset.php, Path.php, Template.php), it looks systemic rather than a single typo.

Temporary workaround (not a real fix)
As a temporary workaround, we can prevent the fatal by adding fallbacks like:

$t4BaseUri = defined('T4PATH_BASE_URI') ? T4PATH_BASE_URI : \Joomla\CMS\Uri\Uri::root(true);

and replacing direct constant usage with the computed variables.
However, this is clearly not ideal: it is patching core plugin files and does not address the underlying cause.

Request
Could you please:
1. Confirm where and when T4 defines the T4PATH* and T4PATH*_URI constants, and
2. Fix the initialization order (or always-define logic) so these constants are guaranteed to exist before T4 classes reference them?

Thanks

4creator

Hello again,

I would like to add an important detail about when this error occurs.

This issue does not happen during normal frontend page rendering.

It happens specifically when using the TinyMCE editor in Joomla:
1. In the Joomla administrator, open an article for editing (TinyMCE).
2. Click an editor-xtd button below the editor (provided by an extension).
3. Joomla opens a modal popup window (tmpl=component style view).
4. At that moment, the popup crashes with fatal errors such as:

•	Undefined constant T4PATH_BASE
•	Undefined constant T4PATH_LOCAL
•	Undefined constant T4PATH_BASE_URI

Switching the site template from T4 to Cassiopeia avoids the crash.

So it seems that in this modal/component rendering context, T4 constants are not initialized before Asset.php, Path.php, and Template.php reference them.

Thank you for checking this specific editor modal scenario.