[4.3] Fix template manager errors on PHP 8.1 and later when having empty parameters

[richard67]

Pull Request for Issue # .

Summary of Changes

When using PHP 8.1 or later and the params value of com_templates is empty in the #__extensions table in database, you get a bunch of PHP errors "Deprecated explode(): Passing null to parameter 2 ($string) of type string is deprecated" in the template manager in backend, and the template manager can not be used, at least that’s the case when error reporting is set to Maximum in global configuration.

The reason is that there are several calls like explode(',', $params->get('image_formats') in the template manager code.

The parameters for which that happens are all of the type "comma-separated list of allowed file name extensions".

This PR here fixes that by using the same default value for each of these parameters which we use for new installation for that parameters.

It's worth a discussion if we should have these default values because it should also be possible to define an empty value for such a list of allowed file name extensions, which currently is not the case due to the default values specified for the fields in the configuration XML. But that should be fixed with a different PR if that's desired.

Testing Instructions

It might need to set error reporting to maximum in global configuration to get the issue.

1. On a 4.3.1 or a current 4.3.2-dev, set the params value to an empty JSON in database, e.g. with phpMyAdmin:

UPDATE `#__extensions` SET `params` = '{}' WHERE `name` = 'com_templates';

You can also test with an empty string:

UPDATE `#__extensions` SET `params` = '' WHERE `name` = 'com_templates';

2. Go to the template manager.
   Result: See section "Actual result BEFORE applying this Pull Request" below.

3. Apply the patch and go again to the template manager or reload the page if still there.
   Result: See section "Expected result AFTER applying this Pull Request" below.

4. Code review: Verify that the default values used in this PR here are the same as in the configuration XML https://github.com/joomla/joomla-cms/blob/4.3-dev/administrator/components/com_templates/config.xml and the installation SQL https://github.com/joomla/joomla-cms/blob/4.3-dev/installation/sql/mysql/base.sql#L174 .

Actual result BEFORE applying this Pull Request

A bunch of PHP errors "Deprecated explode(): Passing null to parameter 2 ($string) of type string is deprecated" in the template manager.

The template manager can not be used, and some quickicon checks in the system panel fail because the overrides check fails.

Expected result AFTER applying this Pull Request

No PHP errors "Deprecated explode(): Passing null to parameter 2 ($string) of type string is deprecated" in the template manager.

The template manager and the quickicon checks in the system panel are working.

Link to documentations

Please select:

• No documentation changes for docs.joomla.org needed

• No documentation changes for manual.joomla.org needed

[TheWhykiki]

I have tested this item ✅ successfully on 70e69da

After applying the Patch, error is fixed.

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[degobbis]

I have tested this item ✅ successfully on 70e69da

Works as expected

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[richard67]

RTC

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[obuisard]

Thank you Richard @richard67 for the PR!

[richard67]

Thanks all.