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Estas 'Perguntas Mias Frequentes' são específicas para o Joomla! 4.0 lançamento Alfa 1. Só serão listados aqui os problemas específicos desta versão, juntamente com as resoluções sugeridas. Por favor, adicione informação para este recurso. O Joomla! Bug Squad irá vigiar esta página para garantir que novos erros sejam adicionados ao monitorizador e resolvidos. Continue a utilizar Joomla! - Fóruns para pedidos de apoio , já que isto não é um substituto para publicar lá, mas sim um local comum para a comunidade reunir problemas comuns de lançamentos.

Bug Squad members, please use the form to the right to create a FAQ page quickly. Try not to use the maintenance version of Joomla in the title as the bug may effect more than one version.

Enter a page title name, then click the button to create.

This Joomla 4 FAQ for extensions developers is a draft, and we are still collecting the questions. TDB questions are “To Be Defined”.

A huge Thank You to our volunteers! This is the current Joomla 4 Beta:

Main Questions

Where is the documentation for migrating from Joomla 3.10.x to Joomla 4?

The Update Working Group is working on documentation as we speak. It’s not ready yet. To get an idea of the process, it will be very similar to the migration process from 2.5 to 3.x. See Why Migrate for details.

Which are the Potential backward compatibility issues in Joomla 4?

This article is the official reference of Potential backward compatibility issues in Joomla 4:

On top of the Potential backward compatibility issues, the biggest change is the new templates based on Bootstrap 4 and other modern front-end tools.

What is Joomla 3.10 compatibility layer?

Joomla 3.10 and Joomla 4 will come with a compatibility layer to easy the transition to Joomla 4. The compatibility layer will be removed on Joomla 5.

For instance, the J-Classes are aliases to the new namespaced classes. JRegistry => \Joomla\Registry\Registry.

What is the Joomla 3.10.x and the Update Checker?

The Update Checker is an extension that will be included on Joomla 3.10 to confirm if:

  • The hosting meets the minimum requirements of Joomla 4.x, and
  • The installed extensions that use the Update Server have versions compatible with Joomla 4.

For more information:

Does Joomla 4 have a compatibility layer for Bootstrap 2.3?

No. All extensions must drop the use of Bootstrap 2.3 in the migration to Joomla 4.

About the Front-end development

Are extensions encouraged to be Framework Agnostic?

That would be ideal but supporting the core backend template, and core front-end template should be a good start. As for the front-end, it would be similar to now.

What have changed on the front-end? Bootstrap? jQuery?

Joomla 4 comes by default with Bootstrap 4 and plain JavaScript scripts. Joomla 4 includes jQuery for backwards compatibility and BS4 compatibility. jQuery is not used at Joomla 4 core level.

Is it defined that Joomla 5 will come with Bootstrap 5?

No. There are no plans about the Framework to be used in Joomla 5 yet.

How does the core team build the front-end files? What has changed?


About The Database Changes

Will Joomla be “NULL date defaults” going forward everywhere?

Yes. This is what is defined in Potential backward compatibility issues in Joomla 4.

Strict mode has been enabled. The following flags are now active by default in Joomla 4 and you may have to update your database queries accordingly. This will help us with future MySQL version upgrades and also aligns more closely with Postgres to enable easier compatibility with queries in both languages.


Will the Joomla 3 to Joomla 4 Updater convert all of the core tables to use “NULL date defaults”?

The Joomla 4 Updater will handle the change of “NULL date defaults” to the new schema. Please, note that the way of how NULL values are managed changes.

These are the upcoming changes:

  1. The 0000-Null conversion
  2. The Null-Mandatory field type conversion, fields that are null on J3 and now they are Mandatory.

For instance, check the following table of field changes:

J3 Table J3 Field name J3 Field type => J4 Table J4 Field name J4 Field type
User registerDate datetime No 0000-00-00 00:00:00 => User registerDate datetime No None
User lastvisitDate datetime No 0000-00-00 00:00:00 => User lastvisitDate datetime Yes NULL
Content created datetime No 0000-00-00 00:00:00 => Content created datetime No None
Content modified datetime No 0000-00-00 00:00:00 => User registerDate modified datetime No None

Please, check the following PR for the Weblinks extension: Fix default value for datetime columns and make some nullable to adapt to CMS 4.0-dev and remove sqlsrv

Will older extensions that still use the “0000-00-00 date defaults” will break?

It depends.

The core upgrade is going to convert only the core tables; and the core upgrade isn’t going to convert schema or content for tables which belong to 3rd-party extensions.

The 3rd-party extension upgrade for Joomla 4 can convert the tables to NULL dates. The extensions will continue to work if using the api for writing into core tables in the right way.

Will the Update Checker check all tables for invalid date defaults?

No, the Update Checker checks the hosting support for Joomla 4 and the availability of extensions for Joomla 4. It will not check individually the tables, only the availability of extensions versions for Joomla 4. Indirectly, the result will be the same.

About PHP Namespaces and Autoloaders

Is the namespacing of extensions mandatory or recommended on Joomla 4?

Namespaced extensions will probably not work in Joomla 3.10 - so you will need to use the non-namespaced extensions if you wish to support Joomla 3.10 and Joomla 4 in the same version.

Using namespaces however is recommended for Joomla 4 native extensions. The use of namespaces will be mandatory for Joomla 5 if you wish to use the core MVC classes.

Can we use still use the current J classes and J helpers in Joomla 4? For instance, JText

Yes. Please, take into account that the J-Classes will be removed on Joomla 5.

Is mandatory the use of namespaces in Joomla 4?


Can an extension without namespaces run on Joomla 4?


Is Joomla 4 organized by PSR4 autoloading?

Yes, the core extensions have a new src folder following the PSR4 namespace organization. However, the autoloader is not driven by a composer.json file.

Ref: PSR-4: Autoloader

Do the legacy autoloaders (jimport and JLoader) work in Joomla 4?


Is Joomla 4 compatible with Composer and Packagist libraries?

Yes, an extension can be developed with Composer libraries, using PSR0, PSR2 or PSR4. Take into account that name and versions collisions can occur between extensions, so techniques to avoid conflicts must be implemented.

What is going to be deprecated on Joomla 5?

Please, check the list of classes that will be deprecated in libraries/classmap.php.

How many autoloaders are active in Joomla 4 by default?


About the extension development

Is there a new recommended extension directory organization?

Yes, this is the new extension organization:

  • forms
  • helpers
  • src
    • Controller
    • Dispatcher
    • Helper
    • Model
    • Service
    • View
  • tmpl

Can an extension follow the Joomla 3 extension organization?


What are the official reference extensions for Joomla 4?

Is there a new priority of view overrides?

TBD. Reference:

What are the services and providers in Joomla 4?


Does Joomla 4 have Container?


Does Joomla 4 have Dependency Injection?


About the security features

What is Joomla 4.0 Content Security Policy (CSP)’s?

Tobias talked about Content Security Policy (CSP) yesterday at JAB 2020. We’ll link the video

How to securely use the Joomla secret