Potentiële terugwaartse compatibiliteitsproblemen in Joomla 4

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Dit document volgt potentiële terugwaartse compatibiliteitsproblemen voor Joomla! 4. Potentiële compatibiliteitsproblemen met extensies worden opgesomd.

De basis voor deze vergelijking is Joomla! 3.9.

Herziene systeemvereisten

De systeemvereisten zijn als volgt bijgewerkt:

  • PHP 7.2
  • MySQL 5.6
  • PostgreSQL 11.0
  • Ondersteuning voor SQL Server is vervallen.

PHP MySQL Extensie

  • Joomla ondersteunt niet langer de PHP ext/mysql driver (die verwijderd is in PHP 7.0). Joomla zal automatisch proberen de mysqli extensie te gebruiken (beschikbaar sinds PHP 5.3). Indien deze niet gevonden wordt zal er geen connectie met de database gemaakt kunnen worden.
  • 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.

As a consequence, Joomla 4 will only use NULL date defaults. The use of the invalid default date of 0000-00-00 00:00:00 in Joomla 4 has been deprecated.

PHP Postgres extensie

  • Joomla! ondersteunt niet langer de ext/pgsql driver van PHP. Joomla! zal automatisch proberen om de PostgreSQL PDO driver (beschikbaar sinds PHP 5.3 en Joomla! 3.9) te gebruiken. Indien deze niet beschikbaar is zal Joomla! geen verbinding met de database kunnen maken.

PHP GMP Extension

This is required for using the WebAuthn Passwordless Login feature. Note the PHP GMP Extension is installed by default on the majority of hosting sites. The WebAuthn Passwordless Login System Plugin is enabled by default in Joomla 4 on https sites.

PHP mcrypt Extension

This is required for using the Joomla\CMS\Crypt\Cipher\CrytoCipher class and its alias JCryptCipherCrypto.

CMS bibliotheken

De volgende wijzigingen zijn gemaakt in de Joomla! CMS bibliotheken (dit is hoofdzakelijk code gevonden in de `libraries/cms` map in Joomla! 3).


  • Plugin installatie via de 'ontdekken' methode zoekt niet langer naar xml bestanden in de Joomla! 1.5 plugin folder layouts.
  • In 3.x, only plugins scripts have the preflight method called and none make postflight available during the uninstall process. All extensions types will have these hooks available in 4.0 when being uninstalled. If you currently preflight and postflight and assume they only apply in an install/update context - this logic is now incorrect and you should use the install route (given as one of the method parameters)
  • Bij het verwijderen van een plugin zal de functie die de plugin verwijdert nu getriggerd worden voordat er SQL queries uitgevoerd worden. Dit is nu consistent met andere extensie types.

Verwijderde classes

De volgende classes zijn in Joomla! 4.0 verwijderd :

  • JInstallerComponent (gebruik hiervoor JInstallerAdapterComponent)
  • JInstallerFile (gebruik hiervoor JInstallerAdapterFile)
  • JInstallerLanguage (gebruik hiervoor JInstallerAdapterLanguage)
  • JInstallerLibrary (gebruik hiervoor JInstallerAdapterLibrary)
  • JInstallerModule (gebruik hiervoor JInstallerAdapterModule)
  • JInstallerPackage (gebruik hiervoor JInstallerAdapterPackage)
  • JInstallerPlugin (gebruik hiervoor JInstallerAdapterPlugin)
  • JInstallerTemplate (gebruik hiervoor JInstallerAdapterTemplate)
  • JSubMenuHelper (gebruik hiervoor JHtmlSidebar; let op dat dit in tegenstelling tot JSubMenuHelper, de toevoeging van een plaatsvervanger in uw template view nodig heeft)

JInstallerAdapter overerving

JInstallerAdapter no longer extends from JAdapterInstance and inherently JObject.

Custom Installer Adapters must now be autoloaded.


JMenu is nu een abstracte class

JMenu is nu een abstracte class. Subclasses van JMenu moeten nu ook een load methode implementeren.

Handmatig include gedrag verwijderd

The logic in JMenu::getInstance() to manually include a file from the application's includes/menu.php path has been removed. The JMenu subclass should be autoloaded instead.


  • You can no longer retrieve the params property from JMenuItem directly. Use the getParams() method instead (available since Joomla 3.7)
  • JMenuItem::set and JMenuItem::get have been removed. Properties must be explicitly named
  • There is now a AdministratorMenuItem class which extends from MenuItem that contains extra public properties used for the Administrator menu item.


  • The magic pagination functions pagination_item_active, pagination_item_inactive have been removed. Use the JLayout's joomla.pagination.link instead
  • The magic pagination function pagination_list_render is deprecated. Use the JLayout joomla.pagination.list instead


Manual Include Behavior verwijderd

The logic in JPathway::getInstance() to manually include a file from the application's includes/pathway.php path has been removed. The JPathway subclass should be autoloaded instead.


Manual Include Behavior Removed

The logic in JRouter::getInstance() to manually include a file from the application's includes/router.php path has been removed. The JRouter subclass should be autoloaded instead.

Method Signature Changes

The attachBuildRule and attachParseRule are now typehinted to require callables.


Ondersteuning voor het benaderen van de JVersion class constanten als class eigenschappen wordt niet langer ondersteund. De constanten werden in Joomla! 3.5 geïntroduceerd om te voorkomen dat de oude class eigenschappen bewerkt konden worden.

De volgende verouderde constanten zijn verwijderd:

  • JVersion::RELEASE
  • JVersion::DEV_LEVEL
  • JVersion::BUILD


  • The register function in JHtml is now typehinted to require a callable. Subclasses of JHtml will now need to match this signature (note this was already required at the function code level already).
  • JHtml::_ no longer allows you to call non-public methods in JHtml
  • JHtml::_ is now a final method (you can no longer override it if you subclass JHtml) and its signature has changed to take advantage of modern PHP features (scalar and variadic typehints)
  • JHtmlBootstrap::modal is verwijderd. Gebruik JHtmlBootstrap::renderModal daarvoor in de plaats.
  • JHtmlSortablelist::sortable has been deprecated in favour of JHtmlDraggablelist::draggable - the old method acts as a proxy to the new method currently to facilitate the removal of jQuery UI from Joomla Core. All media assets relating to the original jQuery UI implementation have been removed.
  • JHtmlBatch has been removed as all the code had been moved to layouts for template overrides. Use the JLayouts directly in your code.


  • We removed the deprecated integer client handling from the updater extension adapter class. Please use site and administrator now and not the integer values 0 / 1.


De volgende wijzigingen zijn gemaakt in de Joomla! CMS bibliotheken (dit is hoofdzakelijk code uit de `libraries/cms` map in Joomla! 3).


  • JAccess::$assetPermissionsById and JAccess::$assetPermissionsByName and JAccess::preloadPermissionsParentIdMapping have been removed without replacement. Since 3.6 we've used other methods and class properties to optimize the loading of assets. See the JAccess bug fixes and optimizations pull request to see the reasons for this deprecation.
  • JAccess::getActions has been removed. Use JAccess::getActionsFromFile or JAccess::getActionsFromData instead.


Verwijderde classes

De volgende classes zijn verwijderd in Joomla! 4.0:

  • JApplicationWebRouter (gebruik hiervoor de `joomla/router` package)
  • JApplicationWebRouterBase (gebruik hiervoor de `joomla/router` package)
  • JApplicationWebRouterRest (gebruik hiervoor de `joomla/router` package)

All references to JSite and JAdministrator have been removed (these were just class alias' since Joomla 3.2)

Verouderde Classes

De volgende classes zijn verouderd en staan ingeplandom in Joomla! 5.0 verwijderd te worden:

  • JApplicationBase (gebruik Joomla\Application\AbstractApplication daarvoor in de plaats)

CLI/Web class wijzigingen

The JApplicationCli and JApplicationWeb classes have been recomposed to extend from the Framework's Application package instead. This breaks type checks for a JApplicationBase object. For forward compatibility, it is recommended to check if application classes are an instance of Joomla\Application\AbstractApplication (JApplicationBase has extended this class since Joomla! 3.4).

Additionally, both of these classes are now abstract. Developers implementing these classes must provide a doExecute method with their application's logic.

The registerEvent method is now typehinted to require a callable for the $handler parameter.

Applications that want to support both Web and CLI Applications should now typehint against the \Joomla\CMS\Application\ CMSApplicationInterface - this contains common methods (some of which in Joomla 3.x were only found in the JApplicationCms class) that can be used by all code. It's strongly recommended any custom applications (especially CLI applications) implement this interface to make compatibility checks easier, simultaneously any typehints should use the interface rather than a concrete class.

  • Oud: JApplicationCli  JApplicationBase   Joomla\Application\AbstractApplication
  • Nieuw: JApplicationCli  Joomla\Application\AbstractCliApplication   Joomla\Application\AbstractApplication
  • Oud: JApplicationWeb  JApplicationBase   Joomla\Application\AbstractApplication
  • Nieuw: JApplicationWeb  Joomla\Application\AbstractWebApplication   Joomla\Application\AbstractApplication
  • The legacy ways of calling JApplicationWeb::redirect have been removed
    • With a message and messageType parameters. (Call enqueueMessage separately.)
    • Passing in a true/false value as the 2nd/3rd parameters instead of a redirect code will give an InvalidArgumentException instead of defaulting to a 303.
  • JApplicationWeb::$singleValueResponseHeaders has been removed because the Framework Application will be internally using PSR-7 Response objects as of its 2.0 release. This changes how the headers data is stored so it is always a multi-dimensional array with each top level key being the header names and the value being an array holding all of the values for that header.
  • The $_clientId, $_messageQueue and $_name class properties have all been renamed to remove their underscore prefix.
  • Implementeert nu CMSApplicationInterface
  • If there is an error retrieving a Pathway, Router or Menu object using the respective methods, the exception will now bubble up rather than the method silently catching the exception and returning null.
  • CMSApplication::getInstance will now additionally try to load the user object (using the loadIdentity function).
  • CMSApplication::isSite and CMSApplication::isAdmin have been removed as with the addition of the ConsoleApplication and ApiApplication can give misleading results. Please use CMSApplication::isClient (available from Joomla  3.7). For more information please see Discover on which client your extension code is running.

De $_language_filter en $_detect_browser class eigenschappen zijn hernoemd om de underscore prefix te verwijderen.

De verouderde methode JApplicationSite::getPageParameters is verwijderd ten gunste van de alias JApplicationSite::getParams


JApplicationHelper::parseXMLLangMetaFile is verwijderd zonder vervanging.


  • The archive package has been removed in favour of the frameworks archive package. Note the API should remain unchanged.
  • De afhandeling van Errors gebruikt nu Exceptions in plaats van JError.


\Joomla\CMS\Client\ClientWrapper has been removed. Use the static methods in \Joomla\CMS\Client\ClientHelper


  • JCrypt::hasStrongPasswordSupport has been removed without replacement as all PHP versions Joomla 4 matches will support strong password hashing.

Verwijderde classes

De volgende Ciphers zijn verwijderd in Joomla! 4.0:

  • JCryptCipher3Des
  • JCryptCipherBlowfish
  • JCryptCipherMcrypt
  • JCryptCipherRijndael256
  • JCryptCipherSimple

Deze zijn verwijderd zonder vervanging. Gebruik JCryptCipherCrypto

Verwijderde Methods

  • JCrypt::hasStrongPasswordSupport has been removed without replacement (this attempted to detect bcrypt polyfills on linux hosting but has always returned true since we required PHP 5.3.10 in Joomla 3.3)


  • JCacheController::get now requires a callable. As a result JCacheControllerCallback::call has been removed.
  • JCacheStorage::test has been removed. Use JCacheStorage::isSupported instead
  • The default storage engines are no longer manually loaded as they are now autoloaded
  • JCacheControllerOutput::start en JCacheControllerOutput::end zijn verwijderd en niet vervangen.
  • CacheLite opslag is verwijderd omdat deze niet compatibel is met PHP7 (de minimum PHP versie voor Joomla! 4)
  • Afhandeling van fouten gebruikt nu Exceptions in plaats van JError.


  • \Joomla\CMS\Component\ComponentRecord breidt niet langer JObject uit.


Verandering in overerving

Van de volgende classes is de overerving veranderd:

  • JDocumentError (now extends from \Joomla\Cms\Document\HtmlDocument instead of \Joomla\Cms\Document\Document)

Note as a result of this change rendering an error page resets the document object in Joomla\CMS\Factory::$document, the rationale being we want a clean document to work from; if the error page is triggered we aren't interested in the metadata your component has set, or the media added from some bad module, or whatever plugins are adding to the display. We want a clean environment for rendering the error page only containing the error page's loaded data.


  • In order to comply with the RSS feed specification, JDocumentRendererFeedRss now allows the lastBuildDate element to be configured using the JDocumentFeed::$lastBuildDate class property when a feed is rendered. This value defaults to the current time, as is the case with Joomla! 3.x and earlier, however the time can be correctly set by changing this class property to a JDate object representing the desired timestamp.
  • There is now a RendererInterface that all Renderers should implement
  • JDocumentRenderer is now an abstract class and implements RendererInterface
  • As an alternative to <jdoc:include type="head" /> you can now individually load <jdoc:include type="metas" /> for metadata, <jdoc:include type="styles" /> for CSS and <jdoc:include type="scripts" /> for JavaScript. The intention of this is to optionally allow users to place all JavaScript at the bottom of the HTML Document in their templates.


The property type of JDocumentFeed::$lastBuildDate has changed from a string to a JDate object. The property was previously unused by the core Joomla API but extensions may have used it.


  • Deze package is vervangen door de Joomla Framework Database Package
  • Debug modus is herschreven (zie de framework docs voor meer informatie). [1])


  • Factory::getApplication no longer takes arguments. These were misleading as it always returned the active application after the first call in the bootstrap, whatever arguments were passed into the function.
  • Factory::getXml is verwijderd, samen met JXMLElement. Gebruik daarvoor in de plaats rechtstreeks SimpleXMLElement.
  • Factory:: getEditor is verwijderd. Gebruik JEditor::getInstance daarvoor in de plaats.


  • JBrowser::isSSLConnection has been removed. Use JApplicationCms::isSSLConnection (available since Joomla 3.2)


  • The filesystem wrapper classes have been removed. Continue using the original static methods.


  • JFilterInput::_remove has been removed in favour of JFilterInput::remove
  • JFilterInput::_cleanTags has been removed in favour of JFilterInput::cleanTags
  • JFilterInput::_cleanAttributes has been removed in favour of JFilterInput::cleanAttributes
  • JFilterInput::_decode has been removed in favour of JFilterInput::decode
  • JFilterInput::_escapeAttributeValues has been removed in favour of JFilterInput::escapeAttributeValues
  • JFilterInput::_stripCSSExpressions has been removed in favour of JFilterInput::stripCSSExpressions

All of the above deprecations and removals are to allow the class to be reunified with the framework parent class.


  • The libraries/joomla/form/fields and libraries/joomla/form/rules directories are no longer registered to find form classes, all form classes should be autoloaded instead
  • Two new properties added addfieldprefix which registers a namespace prefix for extensions (intended to be used as a replacement for addfieldpath). For example usage please see this Github PR
  • JForm::getControlGroup is verwijderd. Gebruik het alias JForm::renderField (beschikbaar sinds Joomla 3.2.3).
  • JForm::getControlGroups is verwijderd. Gebruik het alias JForm::renderFieldset (beschikbaar sinds Joomla 3.2.3).
  • When rendering a field using the hiddenLabel option in JForm - it now only hides the label from the User Interface - the html is still rendered with the sr-only class for screen-reader accessibility purposes.
  • JFormFieldUsergroup is verwijderd. Gebruik Joomla\CMS\Form\Field\UsergrouplistField daarvoor in de plaats (beschikbaar sinds Joomla 3.2).


  • JFormFieldFilelist and JFormFieldFolderList have had their filter properties renamed to fileFilter and folderFilter respectively (in order to allow the use of the regular Joomla filter attribute on returned values)
  • JFormPredefinedlistField has its filter properties renamed to optionsFilter (in order to allow the use of the regular Joomla filter attribute on returned values)
  • JFormFieldEditor::save has been removed without replacement
  • JFormFieldText::getSuggestions has been removed in favour of JFormFieldText::getOptions


  • The form wrapper classes have been removed. Continue using the original static methods.


Verouderde classes en interfaces

De volgende classes en interfaces zijn verouderd en staan op de nominatie om in Joomla! 5.0 verwijderd te worden:

  • JHttpResponse (gebruik Joomla\Http\Response hiervoor in de plaats)
  • JHttpTransport (pas Joomla\Http\TransportInterface toe hiervoor in de plaats)

Verandering in de classes

The Framework's HTTP package is now included in Joomla! 4.0 and JHttp and the JHttpTransport subclasses have been refactored to use the upstream package.


The JHttp class constructor has been loosened with the following changes:

  • The options parameter is no longer typehinted as a Joomla\Registry\Registry object, an array or any object implementing the ArrayAccess interface can be used instead
  • The transport parameter now allows any Joomla\Http\TransportInterface object.

The now deprecated JHttpTransport interface extends Joomla\Http\TransportInterface now and has caused backward compatibility breaking changes in the interface. The constructor is no longer part of the interface, and the interface's `request()` method has had a signature change. Specifically, the second parameter which previously typehinted the JUri class now typehints Joomla\Uri\UriInterface.


In refactoring the response object to inherit from the Framework's HTTP package, which is now using the PSR-7 ResponseInterface API, a minor compatibility break has been made in the structure of the response headers. As of 4.0, this will now always be a multi-dimensional array where the key is the header name and the value is an array of values for that header (previously, this was a string).


Verouderde classes en interfaces

De volgende classes en interfaces zijn verouderd en voor verwijdering ingepland voor verwijdering in Joomla! 5.0:

  • JImageFilter (gebruik Joomla\Image\ImageFilter hiervoor in de plaats)
  • JImageFilterBackgroundfill (gebruik Joomla\Image\Filter\Backgroundfill hiervoor in de plaats)
  • JImageFilterBrightness (gebruik Joomla\Image\Filter\Brightness hiervoor in de plaats)
  • JImageFilterContrast (gebruik Joomla\Image\Filter\Contrast hiervoor in de plaats)
  • JImageFilterEdgedetect (gebruik Joomla\Image\Filter\Edgedetect hiervoor in de plaats)
  • JImageFilterEmboss (gebruik Joomla\Image\Filter\Emboss hiervoor in de plaats)
  • JImageFilterGrayscale (gebruik Joomla\Image\Filter\Grayscale hiervoor in de plaats)
  • JImageFilterNegate (gebruik Joomla\Image\Filter\Negate hiervoor in de plaats)
  • JImageFilterSketchy (gebruik Joomla\Image\Filter\Sketchy hiervoor in de plaats)
  • JImageFilterSmooth (gebruik Joomla\Image\Filter\Smooth hiervoor in de plaats)

Class veranderingen

The classes from Framework's Image package have been inlined into CMS and JImage and the JImageFilter subclasses have been refactored to use them. I.e. all classes under Joomla\Image namespace moved to Joomla\CMS\Image namespace.


  • JMenu::$_items, JMenu::$_default and JMenu::$_active have been had their underscore prefix's removed (note these properties were protected so this only affects custom subclasses of JMenu)

New MVC Layer

  • This has been removed in Joomla 4. We have decided that this effort was not successful and as a result have continued development work on the original MVC Layer (see the "Legacy MVC" section). There is a plugin located on GitHub you can ship with your extensions whilst you migrate them back to the Legacy MVC (note that this is not shipped by default in Joomla 4).


Removing the keychain with 4.0 has resulted in the removal of the following class:

  • JKeychain


  • JPathway::$_pathway and JPathway::$_count have been had their underscore prefix's removed (note these properties were protected so this only affects custom subclasses of JPathway)
  • JPathway::_makeItem has been removed in favour of JPathway::makeItem (note this method was protected so this only affects custom subclasses of JPathway)


  • JProfiler::getmicrotime and JProfiler::getMemory have been removed in favour of the native PHP methods they wrapped (microtime(1) and memory_get_usage() respectively


  • JTable::__construct database object is now typehinted to be a JDatabaseDriver.
    • Subclasses of JTable will need to ensure they are passing a JDatabaseDriver object to the parent constructor
    • Subclasses of JTable will need to change the method signature of setDbo() if they have an extended version of that method to include the typehint
  • There is a new method JTable::hasField - all instances of property_exists on JTable instances will now use this proxy method instead to allow better interoperability of Table instances
  • The JTableObserver pattern (and corresponding classes) has been removed from JTable. JTable now triggers events and Tags, Content History (and any other custom uses of this pattern) should move to standard plugins.


De volgende methods zijn verwijderd in Joomla! 4.0:

  • JMail::sendAdminMail is verwijderd


JMail no longer catches exceptions from PHPMailer. It is now the object calling JMail's responsibility to handle these exceptions as appropriate. In addition if mail sending is disabled in global configuration calling \ Joomla\CMS\Mail\Mail::send() will throw a \Joomla\CMS\Mail\Exception\MailDisabledException.


  • The functions setTransliterator, setPluralSuffixesCallback, setIgnoredSearchWordsCallback, setLowerLimitSearchWordCallback, setUpperLimitSearchWordCallback and setSearchDisplayedCharactersNumberCallback are now typehinted to require a callable.
  • The "_QQ_" placeholder for double quotes has been removed (this only existed to work around an old PHP Bug that has been fixed). Escape double quotes if required (i.e. \")
  • The format for language file names has been changes to ease the work in 3rd party translation tools (such as crowdin). INI language files no longer have to contain the language code (i.e. en-GB.com_contact.ini => com_contact.ini), in this case the special case of en-GB.ini has been renamed to joomla.ini in the core language pack. en-GB.xml has been named langmetadata.xml. There is a b/c layer that will continue to read the old Joomla 3 file names throughout Joomla 4.
  • \Joomla\CMS\Language\Multilanguage::getSiteLangs has been removed. Use \Joomla\CMS\Language\LanguageHelper::getInstalledLanguages(0) instead
  • JLanguage::exists has been removed. Use Joomla\CMS\Language\LanguageHelper::exists instead.
  • The wrapper classes JTextWrapper, LanguageHelperWrapper and TransliterateWrapper have been removed. Continue to use the static methods they wrapped.

Legacy MVC Layer

Legacy Controller

  • JControllerLegacy has been removed from the legacy layer, and we no longer intend to remove it or its subclasses in the near future.
  • JControllerLegacy no longer extends JObject. Controllers should not call any of the methods contained in the JObject class.
  • JControllerLegacy implements an interface for multiple task controllers
  • JControllerLegacy::_construct now takes additional arguments. If you were previously getting a Controller object through JControllerLegacy::getInstance you do not need to change your code.
    • Parameter 2: An optional MVCFactoryInterface instance
    • Parameter 3: An optional CMSApplicationInterface instance
    • Parameter 4: An optional Input instance
    • Parameter 5: An optional FormFactoryInterface instance
  • JControllerForm now uses the StringInflector package to determine the list view. This should improve its ability to determine the list view of more view names. If extension developers find that their list view is no longer being found they should manually set the view_list class property in their controller.

Legacy View

  • JViewLegacy has been removed from the legacy layer, and we no longer intend to remove it or its subclasses in the near future.
  • JViewHtml has been split into two classes - AbstractView and HtmlView. Abstract view contains the logic for accessing models and getting the name of the view and is intended to be a base class for non-Html views. Html view contains the same logic as before.
  • There are now two subclasses of JViewHtml - \Joomla\CMS\MVC\View\ListView and \Joomla\CMS\MVC\View\FormView designed to speed up the development of list and form views and reduce code duplication.


  • JLibraryHelper::_load has been removed. Use \Joomla\CMS\Helper\LibraryHelper::loadLibrary instead.


The session package has undergone a major refactoring to use the Framework's Session package. This change primarily affects the internals of the package; changes to the primary public API through the JSession class are minimal.


The old JString class alias has been removed. Use \Joomla\String\StringHelper instead.

Verwijderde classes en interfaces

The following classes and interfaces have been removed in Joomla! 5.0:

  • JSessionExceptionUnsupported
  • JSessionHandlerInterface
  • JSessionHandlerJoomla
  • JSessionHandlerNative
  • JSessionStorage
  • JSessionStorageApc
  • JSessionStorageDatabase
  • JSessionStorageMemcache
  • JSessionStorageMemcached
  • JSessionStorageNone
  • JSessionStorageWincache
  • JSessionStorageXcache


JSession now extends from the Framework's Joomla\Session\Session class. Many of the methods have a modified signature and a compatibility layer exists to help with the transition.

Namespace parameter verouderd

The get, set, has and clear methods previously supported a namespace parameter. This parameter is now deprecated. The namespace should be prepended to the name before calling these methods.

JSession::clear() Repurposed

In the Joomla\Session\Session class, the clear method is used to clear all data from the session store. In JSession, this method is used to remove a single key. When this method is called with parameters, it will call the new Joomla\Session\Session::remove() method.

JSession::getInstance() verouderd

The singleton getInstance() method has been deprecated. The session object should be retrieved from the active application or the dependency injection container instead.

Sessie handlers

In Joomla! 3.x and earlier, session handlers were represented by the JSessionStorage class and its subclasses. In Joomla! 4.0, session handlers are now implementations of Joomla\Session\HandlerInterface (which is an extension of PHP's SessionHandlerInterface. All handlers which were supported in Joomla! 3.x are still available in 4.0 in addition to two additional handlers: a handler natively implementing the APCu extension and a handler supporting Redis.

Social Media bibliotheken

The facebook, github, google, linkedin, openstreetmap, mediawiki and twitter packages have all been removed from the CMS.


  • JUser::getParameters has been removed. You can no longer retrieve all parameters for a user but instead use JUser::getParam to get individual parameters as required.


  • JUserHelper::getCryptedPassword has been removed. Joomla 4 only supports hashing with the native PHP password_hash function (via JUserHelper::hashPassword (available since Joomla 3.2.1))
  • JUserHelper::getSalt has been removed without replacement (it generated the hash's JUserHelper::getCryptedPassword which is now removed as above)
  • JUserHelper::invalidateCookie, JUserHelper::clearExpiredTokens and JUserHelper::getRememberCookieData have been removed without replacement. They had been unused in core since Joomla 3.2 when their logic was moved into the Cookie Authentication Plugin
  • JUserWrapperHelper has been removed. Continue using the original static methods in JUserHelper.

Classes Removed Without Replacement

  • JNode
  • JTree
  • JGrid
  • JError (use native exceptions when error handling is required)


Verwijderde classes en interfaces

The following classes and interfaces have been removed in Joomla! 4.0:

  • JArrayHelper

use Joomla\Utilities\ArrayHelper; instead.

Externe bibliotheken

The following changes have been made to the external libraries that Joomla! packages and ships.


Joomla! 4.0 ships with PHPMailer 6.0. Please review the upgrading guide for relevant changes.


At Joomla! 3.4, the PHPUTF8 library lived in two locations in the Joomla! package; `libraries/phputf8` and `libraries/vendor/joomla/string/src/phputf8`. In Joomla! 4.0, the copy of the library in `libraries/phputf8` has been removed. The Joomla\String\StringHelper class exposes many of the library's functions and the Composer autoloader definition imports much of the library as well, however, if you need a feature that is not already included then you should import the required functions from the `libraries/vendor/joomla/string/src/phputf8` path.


The SimplePie library is no longer included with Joomla! 4.0.


Joomla! 4.0 ships with jQuery 3. Please review the upgrading guide for relevant changes. Note that we are not including jQuery Migrate anymore either. We recommend using it locally to help debug your code if there are any issues.

jQuery UI

jQuery UI has been removed from Joomla 4. Whilst it hasn't been officially announced as dead, there hasn't been a release of jQuery UI since 2016.


Joomla! 4.0 ships with Bootstrap 4. Bootstrap 2.3.2 has been removed, however we have left some BS2 classes in to ease the migration (e.g. The old BS2 element-invisible still exists for screenreaders)


FOF 2.x has been removed.


All the Joomla! 3 templates - ISIS and Hathor in the backend, and Protostar and Beez in the frontend are no longer supported. The new 4.0 backend template is called Atum and the frontend template is called Cassiopeia.

As a consequence, all extensions must migrate to the new Bootstrap 4 style, away from the current Bootstrap 2.3.2 implementation. For more information about Bootstrap, visit the Bootstrap 4 Website and the Bootstrap 2.3.2 Website.

  • Joomla 4 will load the template favicon first rather than the one in the Joomla Root in keeping with the concept the template is the single source of truth.
  • Frontend components and module views now use Block Element Modifier (BEM) class markup to make it easier for templates to support frameworks other than bootstrap. See the BEM Website for more information on how to build similar classes.

There where also changes to options of the core components that you should take a look at when your tempalte should support 3.x and 4.x at the same time: https://docs.joomla.org/J4.x:Changed_parameters_for_template_providers


  • The $_PROFILER global variable has been removed. Use \Joomla\CMS\Profiler\Profiler::getInstance instead.

Media in Libraries

No media is allowed in the libraries root folder in the CMS. All assets associated with Joomla libraries should be put in the media folder per best practices. Direct access is blocked with a .htaccess and the web.config file in the root of the libraries directory.


Removing the keychain with 4.0 has resulted in the removal of the entire Bin directory as it only contained keychain.


  • All components have been namespaced and directories reworked accordingly. For more information about this read the tutorial on building a component in Joomla 4.
  • com_admin profile view has been removed. (This appears to have been created historically due to issues accessing com_users. This is no longer the case so all user edits go through com_users edit user view in the backend.)
  • com_actionlogs PHP 5.5 backfill code has been removed and accordingly ActionlogsHelper::getCsvData() is now type hinted to return a Generator object
  • com_actionlogs CSV export headers have been changed to match the strings shown in the UI.
  • Core components have had URL Routing 'Legacy' mode removed from Joomla 3.7. You should either use your .htaccess file or the redirect component to fix any internal URLs that change. You can try the 'Modern' mode in Joomla 3 by following the instructions here
  • The MailTo component has been removed without replacement. If you used this functionality you will need to find an alternative component on JED.
  • In com_contact 's frontend contact view - the contact property has been removed as it was a duplicate of the item property. We chose to keep $this->item as it was consistent with that in the article and tag views. Template overrides will need updating to reflect this.
  • The repeatable field in com_fields has been removed in favour of the new subform field. Data from repeatable fields is automatically migrated to the new subform field but is stored in a different format.
  • The xreference fields have been removed from #__contact_details, #__content and #__newsfeeds as they were unused.


  • The Gmail authentication plugin has been removed. For more information please read this blog post
  • Google reCAPTCHA v1 support has been fully removed from the CAPTCHA plugin. This hasn't worked since Q2 2018. Google dropped support for it.
  • The reCAPTCHA plugin now uses Google's official PHP library for CAPTCHA under the hood
  • For plugins using the 3.x compatibility layer, the name result is a protected property for both input parameters and return values. For information on the new recommended approach to plugins please read S:MyLanguage/J4.x:Creating_a_Plugin_for_Joomla
  • For plugins using the 3.x compatibility layer, for any type hints for events that require a class, that class must be autoloaded before the plugin is instantiated.
  • The onContentBeforeSave event now requires the data parameter. This has been passed in \Joomla\CMS\MVC\Model\LegacyModel since 3.7 but is now passed in consistently by core extensions and used by the core Joomla content plugin.
  • Returning before calling parent::__construct() in the constructor of a plugin is no longer supported to avoid queuing the plugin into the event dispatcher.
  • onUserBeforeDataValidation is deprecated as an event in favor of onContentBeforeValidateData (The event was usable by all content types and was not specific to users. Note that both events will be called for the duration of Joomla 4. You should migrate your code to the new event when you no longer need to support Joomla 3.

Administrator Helpers

  • JAdministratorHelper has been removed without replacement. (It's been merged into JApplicationAdministrator.)
  • JSubMenuHelper has been removed without replacement. (Use JHtmlSidebar instead - available since 3.0.)
  • JToolbarHelper has been moved to the main libraries directory.


  • The administrator module submenu has been removed.
  • Logic of Module Chromes (module styles) in template files html/modules.php have been moved to JLayout files. modChrome_x functions in modules.php are no longer supported. See https://github.com/joomla/joomla-cms/pull/23570 for details.
  • Module Chromes (module styles) modChrome_horz, modChrome_xhtml, modChrome_rounded have been removed from template system without replacement.
  • Module Class Suffixes have been renamed and standardized. These are now called Module Class and are appended to the list of classes in the Module Chrome. (They are no longer rendered in the module output itself.)

Error afhandeling

  • Joomla will now handle PHP's E_USER_DEPRECATED errors and pipes it into JLog - this is useful for handling deprecations in many 3rd party PHP Libraries (note it will block the page load if debug mode is enabled)
  • Joomla\CMS\Exception\ExceptionHandler now only operates on Exceptions thrown in JApplication::execute. We now use Symfony's ErrorHandler when this fails or exceptions are thrown outside of this. We expect this to have minimal effect on most users and should give a more helpful message in many cases than the traditional "Error displaying the error page" error for users when things go very wrong.
  • Joomla\CMS\Exception\ExceptionHandler is now format aware and will render errors in html, json, xml, feed or cli aware formats
  • The Joomla\CMS\Exception\ExceptionHandler::render() signature is changed to include the Throwable typehint. Before 3.5 when PHP 7 support was added this was typehinted as Exception, and since 3.5 has been typechecked in the code itself.

Base Tag

Previous Joomla versions set a <base> header tag of the current URL in the frontend. This has been removed as it served no clear purpose.


The caption.js file has been removed from Joomla. Use the native HTML elements figure and figcaption. (You can look at JLayout in layouts/joomla/content/intro_image.php for an example).


Class usage like $msg = JText::_( 'Hello man!' ); can now use namespacing. That would turn into $msg = Text::_( 'Hello man!' );. To use namespacing, you need to add the proper namespace declaration. This should be added after the defined('_JEXEC') or die;.

To find out the proper namespace you can either follow the instructions here: SO confused about namespace & enquemessage... or use the generated file pdf reference file: File:J! namespace reference.pdf