How many Components, modules & MVC issues are in this guide?

This guide covers 28 catalog entries with before/after replacements.

Joomla Components, modules & MVC changes: Joomla 3 → 4, 5 and 6

28 issues in this guide

Components and modules share the MVC rename map. This guide groups 28 entries: FOFModel / FOFTable, JCategories, JCategoryNode, JComponentHelper, JControllerAdmin, JControllerForm, JControllerLegacy, JHelper, JHelperContent, JHelperTags, and 18 more. The replacement pattern is the Joomla\CMS\MVC\* tree — BaseController, AdminController, FormController, ListModel, AdminModel, FormModel, HtmlView — plus ComponentHelper and ModuleHelper. getInstance() string factories give way to MVCFactory / $this->getModel(). assignRef disappears; assign public view properties. setError / getError become exceptions. FOF2 is not in Joomla 4 core; upgrade the library or rewrite. Hop mix: 4 at Joomla 3 → 4; 24 at Joomla 5 → 6. Work one MVC layer at a time on staging: controllers and models first, then views and helpers, using each entry's before/after as the checklist from the catalog. Catalog replacements in this guide include FOFModel / FOFTable → FOF 3 / native Joomla MVC; JCategories → Joomla\CMS\Categories\Categories; JCategoryNode → Joomla\CMS\Categories\CategoryNode; JComponentHelper → Joomla\CMS\Component\ComponentHelper. Open each h2 anchor for the full before/after, fix list, and error strings shipped in the reference data.

FOF2-001

FOFModel / FOFTable

FOF 2.x in core

Framework-on-Framework 2 shipped with some J3 stacks and is not in Joomla 4 core.

FOFModel / FOFTable → FOF 3 / native Joomla MVC

Dies at Joomla 3 → 4

Dies at Joomla 3 → 4J3: Works nativelyJ4: Removed — fatalJ6: Removed — fatalBC plugin: no — already dead on J4Architecture change — no auto-fixMVC

What you will see

Class "FOFModel" not found
Class "FOFTable" not found

Symptoms people search

Akeeba/FOF component 500 · FOFModel

Replace this code

Swap FOFModel / FOFTable for FOF 3 / native Joomla MVC.

Joomla 3

Remove or stop calling this

class LmsModelCourses extends FOFModel {}

Joomla 4 / 6

Use this instead

Port to FOF 3 or to namespaced ListModel/AdminModel. FOF 2 is not in Joomla 4.

How to fix it

1Upgrade the FOF library to a J4+ release or rewrite MVC.

Also known as

FOF · FOFModel · FOFTable · FOFForm

There is no 1:1 swap for this one. The architecture changed. If you cannot rewrite it, Infyways can.

Scan a ZIP for this Ask Infyways to fix it

JCATEGORIES-CLASS-001

JCategories

JCategories class name

JCategories is a Joomla 3 global class. Joomla 4 still has an alias. Joomla 5 needs the Behaviour – Backward Compatibility plugin. Native Joomla 6 does not load that alias — you get Class "JCategories" not found.

JCategories → Joomla\CMS\Categories\Categories

Dies at Joomla 5 → 6

Dies at Joomla 5 → 6J3: Works nativelyJ4: Alias (old name still resolves)J6: Removed — fatalBC plugin: covers the class nameMechanical renameJoomla API

What you will see

Class "JCategories" not found
Class 'JCategories' not found
Failed to open stream: JCategories

Symptoms people search

white screen after disabling compatibility plugin · class not found on Joomla 6 · works on Joomla 5 until I turn off backward compatibility

Replace this code

Swap JCategories for Joomla\CMS\Categories\Categories.

Joomla 3

Remove or stop calling this

JCategories::getInstance();
// or new JCategories()

Joomla 4 / 6

Use this instead

use Joomla\CMS\Categories\Categories;

// Call the namespaced class. Do not keep the J prefix.

How to fix it

1Add a use statement for Joomla\CMS\Categories\Categories.
2Replace every JCategories with the short class name from that use line.
3Disable Behaviour – Backward Compatibility on a Joomla 5 staging site. If it fatals, this class is still in the code.

Also known as

JCategories · Joomla\CMS\Categories\Categories · class alias · J prefix

Scan a ZIP for this Ask Infyways to fix it

JCATEGORYNODE-CLASS-001

JCategoryNode

JCategoryNode class name

JCategoryNode is a Joomla 3 global class. Joomla 4 still has an alias. Joomla 5 needs the Behaviour – Backward Compatibility plugin. Native Joomla 6 does not load that alias — you get Class "JCategoryNode" not found.

JCategoryNode → Joomla\CMS\Categories\CategoryNode

Dies at Joomla 5 → 6

Dies at Joomla 5 → 6J3: Works nativelyJ4: Alias (old name still resolves)J6: Removed — fatalBC plugin: covers the class nameMechanical renameJoomla API

What you will see

Class "JCategoryNode" not found
Class 'JCategoryNode' not found
Failed to open stream: JCategoryNode

Symptoms people search

white screen after disabling compatibility plugin · class not found on Joomla 6 · works on Joomla 5 until I turn off backward compatibility

Replace this code

Swap JCategoryNode for Joomla\CMS\Categories\CategoryNode.

Joomla 3

Remove or stop calling this

JCategoryNode::getInstance();
// or new JCategoryNode()

Joomla 4 / 6

Use this instead

use Joomla\CMS\Categories\CategoryNode;

// Call the namespaced class. Do not keep the J prefix.

How to fix it

1Add a use statement for Joomla\CMS\Categories\CategoryNode.
2Replace every JCategoryNode with the short class name from that use line.
3Disable Behaviour – Backward Compatibility on a Joomla 5 staging site. If it fatals, this class is still in the code.

Also known as

JCategoryNode · Joomla\CMS\Categories\CategoryNode · class alias · J prefix

Scan a ZIP for this Ask Infyways to fix it

JCOMPONENTHELPER-CLASS-001

JComponentHelper

JComponentHelper class name

JComponentHelper is a Joomla 3 global class. Joomla 4 still has an alias. Joomla 5 needs the Behaviour – Backward Compatibility plugin. Native Joomla 6 does not load that alias — you get Class "JComponentHelper" not found.

JComponentHelper → Joomla\CMS\Component\ComponentHelper

Dies at Joomla 5 → 6

Dies at Joomla 5 → 6J3: Works nativelyJ4: Alias (old name still resolves)J6: Removed — fatalBC plugin: covers the class nameMechanical renameJoomla API

What you will see

Class "JComponentHelper" not found
Class 'JComponentHelper' not found
Failed to open stream: JComponentHelper

Symptoms people search

white screen after disabling compatibility plugin · class not found on Joomla 6 · works on Joomla 5 until I turn off backward compatibility

Replace this code

Swap JComponentHelper for Joomla\CMS\Component\ComponentHelper.

Joomla 3

Remove or stop calling this

JComponentHelper::getInstance();
// or new JComponentHelper()

Joomla 4 / 6

Use this instead

use Joomla\CMS\Component\ComponentHelper;

// Call the namespaced class. Do not keep the J prefix.

How to fix it

1Add a use statement for Joomla\CMS\Component\ComponentHelper.
2Replace every JComponentHelper with the short class name from that use line.
3Disable Behaviour – Backward Compatibility on a Joomla 5 staging site. If it fatals, this class is still in the code.

Also known as

JComponentHelper · Joomla\CMS\Component\ComponentHelper · class alias · J prefix

Scan a ZIP for this Ask Infyways to fix it

JCONTROLLERADMIN-CLASS-001

JControllerAdmin

JControllerAdmin class name

JControllerAdmin is a Joomla 3 global class. Joomla 4 still has an alias. Joomla 5 needs the Behaviour – Backward Compatibility plugin. Native Joomla 6 does not load that alias — you get Class "JControllerAdmin" not found.

JControllerAdmin → Joomla\CMS\MVC\Controller\AdminController

Dies at Joomla 5 → 6

Dies at Joomla 5 → 6J3: Works nativelyJ4: Alias (old name still resolves)J6: Removed — fatalBC plugin: covers the class nameMechanical renameMVC

What you will see

Class "JControllerAdmin" not found
Class 'JControllerAdmin' not found
Failed to open stream: JControllerAdmin

Symptoms people search

white screen after disabling compatibility plugin · class not found on Joomla 6 · works on Joomla 5 until I turn off backward compatibility

Replace this code

Swap JControllerAdmin for Joomla\CMS\MVC\Controller\AdminController.

Joomla 3

Remove or stop calling this

JControllerAdmin::getInstance();
// or new JControllerAdmin()

Joomla 4 / 6

Use this instead

use Joomla\CMS\MVC\Controller\AdminController;

// Call the namespaced class. Do not keep the J prefix.

How to fix it

1Add a use statement for Joomla\CMS\MVC\Controller\AdminController.
2Replace every JControllerAdmin with the short class name from that use line.
3Disable Behaviour – Backward Compatibility on a Joomla 5 staging site. If it fatals, this class is still in the code.

Also known as

JControllerAdmin · Joomla\CMS\MVC\Controller\AdminController · class alias · J prefix

Scan a ZIP for this Ask Infyways to fix it

JCONTROLLERFORM-CLASS-001

JControllerForm

JControllerForm class name

JControllerForm is a Joomla 3 global class. Joomla 4 still has an alias. Joomla 5 needs the Behaviour – Backward Compatibility plugin. Native Joomla 6 does not load that alias — you get Class "JControllerForm" not found.

JControllerForm → Joomla\CMS\MVC\Controller\FormController

Dies at Joomla 5 → 6

Dies at Joomla 5 → 6J3: Works nativelyJ4: Alias (old name still resolves)J6: Removed — fatalBC plugin: covers the class nameMechanical renameMVC

What you will see

Class "JControllerForm" not found
Class 'JControllerForm' not found
Failed to open stream: JControllerForm

Symptoms people search

white screen after disabling compatibility plugin · class not found on Joomla 6 · works on Joomla 5 until I turn off backward compatibility

Replace this code

Swap JControllerForm for Joomla\CMS\MVC\Controller\FormController.

Joomla 3

Remove or stop calling this

JControllerForm::getInstance();
// or new JControllerForm()

Joomla 4 / 6

Use this instead

use Joomla\CMS\MVC\Controller\FormController;

// Call the namespaced class. Do not keep the J prefix.

How to fix it

1Add a use statement for Joomla\CMS\MVC\Controller\FormController.
2Replace every JControllerForm with the short class name from that use line.
3Disable Behaviour – Backward Compatibility on a Joomla 5 staging site. If it fatals, this class is still in the code.

Also known as

JControllerForm · Joomla\CMS\MVC\Controller\FormController · class alias · J prefix

Scan a ZIP for this Ask Infyways to fix it

JCONTROLLERLEGACY-CLASS-001

JControllerLegacy

JControllerLegacy class name

JControllerLegacy is a Joomla 3 global class. Joomla 4 still has an alias. Joomla 5 needs the Behaviour – Backward Compatibility plugin. Native Joomla 6 does not load that alias — you get Class "JControllerLegacy" not found.

JControllerLegacy → Joomla\CMS\MVC\Controller\BaseController

Dies at Joomla 5 → 6

Dies at Joomla 5 → 6J3: Works nativelyJ4: Alias (old name still resolves)J6: Removed — fatalBC plugin: covers the class nameMechanical renameMVC

What you will see

Class "JControllerLegacy" not found
Class 'JControllerLegacy' not found
Failed to open stream: JControllerLegacy

Symptoms people search

white screen after disabling compatibility plugin · class not found on Joomla 6 · works on Joomla 5 until I turn off backward compatibility

Replace this code

Swap JControllerLegacy for Joomla\CMS\MVC\Controller\BaseController.

Joomla 3

Remove or stop calling this

JControllerLegacy::getInstance();
// or new JControllerLegacy()

Joomla 4 / 6

Use this instead

use Joomla\CMS\MVC\Controller\BaseController;

// Call the namespaced class. Do not keep the J prefix.

How to fix it

1Add a use statement for Joomla\CMS\MVC\Controller\BaseController.
2Replace every JControllerLegacy with the short class name from that use line.
3Disable Behaviour – Backward Compatibility on a Joomla 5 staging site. If it fatals, this class is still in the code.

Also known as

JControllerLegacy · Joomla\CMS\MVC\Controller\BaseController · class alias · J prefix

Scan a ZIP for this Ask Infyways to fix it

JHELPER-CLASS-001

JHelper

JHelper class name

JHelper is a Joomla 3 global class. Joomla 4 still has an alias. Joomla 5 needs the Behaviour – Backward Compatibility plugin. Native Joomla 6 does not load that alias — you get Class "JHelper" not found.

JHelper → Joomla\CMS\Helper\CMSHelper

Dies at Joomla 5 → 6

Dies at Joomla 5 → 6J3: Works nativelyJ4: Alias (old name still resolves)J6: Removed — fatalBC plugin: covers the class nameMechanical renameJoomla API

What you will see

Class "JHelper" not found
Class 'JHelper' not found
Failed to open stream: JHelper

Symptoms people search

white screen after disabling compatibility plugin · class not found on Joomla 6 · works on Joomla 5 until I turn off backward compatibility

Replace this code

Swap JHelper for Joomla\CMS\Helper\CMSHelper.

Joomla 3

Remove or stop calling this

JHelper::getInstance();
// or new JHelper()

Joomla 4 / 6

Use this instead

use Joomla\CMS\Helper\CMSHelper;

// Call the namespaced class. Do not keep the J prefix.

How to fix it

1Add a use statement for Joomla\CMS\Helper\CMSHelper.
2Replace every JHelper with the short class name from that use line.
3Disable Behaviour – Backward Compatibility on a Joomla 5 staging site. If it fatals, this class is still in the code.

Also known as

JHelper · Joomla\CMS\Helper\CMSHelper · class alias · J prefix

Scan a ZIP for this Ask Infyways to fix it

JHELPERCONTENT-CLASS-001

JHelperContent

JHelperContent class name

JHelperContent is a Joomla 3 global class. Joomla 4 still has an alias. Joomla 5 needs the Behaviour – Backward Compatibility plugin. Native Joomla 6 does not load that alias — you get Class "JHelperContent" not found.

JHelperContent → Joomla\CMS\Helper\ContentHelper

Dies at Joomla 5 → 6

Dies at Joomla 5 → 6J3: Works nativelyJ4: Alias (old name still resolves)J6: Removed — fatalBC plugin: covers the class nameMechanical renameJoomla API

What you will see

Class "JHelperContent" not found
Class 'JHelperContent' not found
Failed to open stream: JHelperContent

Symptoms people search

white screen after disabling compatibility plugin · class not found on Joomla 6 · works on Joomla 5 until I turn off backward compatibility

Replace this code

Swap JHelperContent for Joomla\CMS\Helper\ContentHelper.

Joomla 3

Remove or stop calling this

JHelperContent::getInstance();
// or new JHelperContent()

Joomla 4 / 6

Use this instead

use Joomla\CMS\Helper\ContentHelper;

// Call the namespaced class. Do not keep the J prefix.

How to fix it

1Add a use statement for Joomla\CMS\Helper\ContentHelper.
2Replace every JHelperContent with the short class name from that use line.
3Disable Behaviour – Backward Compatibility on a Joomla 5 staging site. If it fatals, this class is still in the code.

Also known as

JHelperContent · Joomla\CMS\Helper\ContentHelper · class alias · J prefix

Scan a ZIP for this Ask Infyways to fix it

JHELPERTAGS-CLASS-001

JHelperTags

JHelperTags class name

JHelperTags is a Joomla 3 global class. Joomla 4 still has an alias. Joomla 5 needs the Behaviour – Backward Compatibility plugin. Native Joomla 6 does not load that alias — you get Class "JHelperTags" not found.

JHelperTags → Joomla\CMS\Helper\TagsHelper

Dies at Joomla 5 → 6

Dies at Joomla 5 → 6J3: Works nativelyJ4: Alias (old name still resolves)J6: Removed — fatalBC plugin: covers the class nameMechanical renameJoomla API

What you will see

Class "JHelperTags" not found
Class 'JHelperTags' not found
Failed to open stream: JHelperTags

Symptoms people search

white screen after disabling compatibility plugin · class not found on Joomla 6 · works on Joomla 5 until I turn off backward compatibility

Replace this code

Swap JHelperTags for Joomla\CMS\Helper\TagsHelper.

Joomla 3

Remove or stop calling this

JHelperTags::getInstance();
// or new JHelperTags()

Joomla 4 / 6

Use this instead

use Joomla\CMS\Helper\TagsHelper;

// Call the namespaced class. Do not keep the J prefix.

How to fix it

1Add a use statement for Joomla\CMS\Helper\TagsHelper.
2Replace every JHelperTags with the short class name from that use line.
3Disable Behaviour – Backward Compatibility on a Joomla 5 staging site. If it fatals, this class is still in the code.

Also known as

JHelperTags · Joomla\CMS\Helper\TagsHelper · class alias · J prefix

Scan a ZIP for this Ask Infyways to fix it

JMODELADMIN-CLASS-001

JModelAdmin

JModelAdmin class name

JModelAdmin is a Joomla 3 global class. Joomla 4 still has an alias. Joomla 5 needs the Behaviour – Backward Compatibility plugin. Native Joomla 6 does not load that alias — you get Class "JModelAdmin" not found.

JModelAdmin → Joomla\CMS\MVC\Model\AdminModel

Dies at Joomla 5 → 6

Dies at Joomla 5 → 6J3: Works nativelyJ4: Alias (old name still resolves)J6: Removed — fatalBC plugin: covers the class nameMechanical renameMVC

What you will see

Class "JModelAdmin" not found
Class 'JModelAdmin' not found
Failed to open stream: JModelAdmin

Symptoms people search

white screen after disabling compatibility plugin · class not found on Joomla 6 · works on Joomla 5 until I turn off backward compatibility

Replace this code

Swap JModelAdmin for Joomla\CMS\MVC\Model\AdminModel.

Joomla 3

Remove or stop calling this

JModelAdmin::getInstance();
// or new JModelAdmin()

Joomla 4 / 6

Use this instead

use Joomla\CMS\MVC\Model\AdminModel;

// Call the namespaced class. Do not keep the J prefix.

How to fix it

1Add a use statement for Joomla\CMS\MVC\Model\AdminModel.
2Replace every JModelAdmin with the short class name from that use line.
3Disable Behaviour – Backward Compatibility on a Joomla 5 staging site. If it fatals, this class is still in the code.

Also known as

JModelAdmin · Joomla\CMS\MVC\Model\AdminModel · class alias · J prefix

Scan a ZIP for this Ask Infyways to fix it

JMODELFORM-CLASS-001

JModelForm

JModelForm class name

JModelForm is a Joomla 3 global class. Joomla 4 still has an alias. Joomla 5 needs the Behaviour – Backward Compatibility plugin. Native Joomla 6 does not load that alias — you get Class "JModelForm" not found.

JModelForm → Joomla\CMS\MVC\Model\FormModel

Dies at Joomla 5 → 6

Dies at Joomla 5 → 6J3: Works nativelyJ4: Alias (old name still resolves)J6: Removed — fatalBC plugin: covers the class nameMechanical renameMVC

What you will see

Class "JModelForm" not found
Class 'JModelForm' not found
Failed to open stream: JModelForm

Symptoms people search

white screen after disabling compatibility plugin · class not found on Joomla 6 · works on Joomla 5 until I turn off backward compatibility

Replace this code

Swap JModelForm for Joomla\CMS\MVC\Model\FormModel.

Joomla 3

Remove or stop calling this

JModelForm::getInstance();
// or new JModelForm()

Joomla 4 / 6

Use this instead

use Joomla\CMS\MVC\Model\FormModel;

// Call the namespaced class. Do not keep the J prefix.

How to fix it

1Add a use statement for Joomla\CMS\MVC\Model\FormModel.
2Replace every JModelForm with the short class name from that use line.
3Disable Behaviour – Backward Compatibility on a Joomla 5 staging site. If it fatals, this class is still in the code.

Also known as

JModelForm · Joomla\CMS\MVC\Model\FormModel · class alias · J prefix

Scan a ZIP for this Ask Infyways to fix it

JMODELITEM-CLASS-001

JModelItem

JModelItem class name

JModelItem is a Joomla 3 global class. Joomla 4 still has an alias. Joomla 5 needs the Behaviour – Backward Compatibility plugin. Native Joomla 6 does not load that alias — you get Class "JModelItem" not found.

JModelItem → Joomla\CMS\MVC\Model\ItemModel

Dies at Joomla 5 → 6

Dies at Joomla 5 → 6J3: Works nativelyJ4: Alias (old name still resolves)J6: Removed — fatalBC plugin: covers the class nameMechanical renameMVC

What you will see

Class "JModelItem" not found
Class 'JModelItem' not found
Failed to open stream: JModelItem

Symptoms people search

white screen after disabling compatibility plugin · class not found on Joomla 6 · works on Joomla 5 until I turn off backward compatibility

Replace this code

Swap JModelItem for Joomla\CMS\MVC\Model\ItemModel.

Joomla 3

Remove or stop calling this

JModelItem::getInstance();
// or new JModelItem()

Joomla 4 / 6

Use this instead

use Joomla\CMS\MVC\Model\ItemModel;

// Call the namespaced class. Do not keep the J prefix.

How to fix it

1Add a use statement for Joomla\CMS\MVC\Model\ItemModel.
2Replace every JModelItem with the short class name from that use line.
3Disable Behaviour – Backward Compatibility on a Joomla 5 staging site. If it fatals, this class is still in the code.

Also known as

JModelItem · Joomla\CMS\MVC\Model\ItemModel · class alias · J prefix

Scan a ZIP for this Ask Infyways to fix it

JMODELLEGACY-CLASS-001

JModelLegacy

JModelLegacy class name

JModelLegacy is a Joomla 3 global class. Joomla 4 still has an alias. Joomla 5 needs the Behaviour – Backward Compatibility plugin. Native Joomla 6 does not load that alias — you get Class "JModelLegacy" not found.

JModelLegacy → Joomla\CMS\MVC\Model\BaseDatabaseModel

Dies at Joomla 5 → 6

Dies at Joomla 5 → 6J3: Works nativelyJ4: Alias (old name still resolves)J6: Removed — fatalBC plugin: covers the class nameMechanical renameMVC

What you will see

Class "JModelLegacy" not found
Class 'JModelLegacy' not found
Failed to open stream: JModelLegacy

Symptoms people search

white screen after disabling compatibility plugin · class not found on Joomla 6 · works on Joomla 5 until I turn off backward compatibility

Replace this code

Swap JModelLegacy for Joomla\CMS\MVC\Model\BaseDatabaseModel.

Joomla 3

Remove or stop calling this

JModelLegacy::getInstance();
// or new JModelLegacy()

Joomla 4 / 6

Use this instead

use Joomla\CMS\MVC\Model\BaseDatabaseModel;

// Call the namespaced class. Do not keep the J prefix.

How to fix it

1Add a use statement for Joomla\CMS\MVC\Model\BaseDatabaseModel.
2Replace every JModelLegacy with the short class name from that use line.
3Disable Behaviour – Backward Compatibility on a Joomla 5 staging site. If it fatals, this class is still in the code.

Also known as

JModelLegacy · Joomla\CMS\MVC\Model\BaseDatabaseModel · class alias · J prefix

Scan a ZIP for this Ask Infyways to fix it

JMODELLIST-CLASS-001

JModelList

JModelList class name

JModelList is a Joomla 3 global class. Joomla 4 still has an alias. Joomla 5 needs the Behaviour – Backward Compatibility plugin. Native Joomla 6 does not load that alias — you get Class "JModelList" not found.

JModelList → Joomla\CMS\MVC\Model\ListModel

Dies at Joomla 5 → 6

Dies at Joomla 5 → 6J3: Works nativelyJ4: Alias (old name still resolves)J6: Removed — fatalBC plugin: covers the class nameMechanical renameMVC

What you will see

Class "JModelList" not found
Class 'JModelList' not found
Failed to open stream: JModelList

Symptoms people search

white screen after disabling compatibility plugin · class not found on Joomla 6 · works on Joomla 5 until I turn off backward compatibility

Replace this code

Swap JModelList for Joomla\CMS\MVC\Model\ListModel.

Joomla 3

Remove or stop calling this

JModelList::getInstance();
// or new JModelList()

Joomla 4 / 6

Use this instead

use Joomla\CMS\MVC\Model\ListModel;

// Call the namespaced class. Do not keep the J prefix.

How to fix it

1Add a use statement for Joomla\CMS\MVC\Model\ListModel.
2Replace every JModelList with the short class name from that use line.
3Disable Behaviour – Backward Compatibility on a Joomla 5 staging site. If it fatals, this class is still in the code.

Also known as

JModelList · Joomla\CMS\MVC\Model\ListModel · class alias · J prefix

Scan a ZIP for this Ask Infyways to fix it

JMODULEHELPER-CLASS-001

JModuleHelper

JModuleHelper class name

JModuleHelper is a Joomla 3 global class. Joomla 4 still has an alias. Joomla 5 needs the Behaviour – Backward Compatibility plugin. Native Joomla 6 does not load that alias — you get Class "JModuleHelper" not found.

JModuleHelper → Joomla\CMS\Helper\ModuleHelper

Dies at Joomla 5 → 6

Dies at Joomla 5 → 6J3: Works nativelyJ4: Alias (old name still resolves)J6: Removed — fatalBC plugin: covers the class nameMechanical renameJoomla API

What you will see

Class "JModuleHelper" not found
Class 'JModuleHelper' not found
Failed to open stream: JModuleHelper

Symptoms people search

white screen after disabling compatibility plugin · class not found on Joomla 6 · works on Joomla 5 until I turn off backward compatibility

Replace this code

Swap JModuleHelper for Joomla\CMS\Helper\ModuleHelper.

Joomla 3

Remove or stop calling this

JModuleHelper::getInstance();
// or new JModuleHelper()

Joomla 4 / 6

Use this instead

use Joomla\CMS\Helper\ModuleHelper;

// Call the namespaced class. Do not keep the J prefix.

How to fix it

1Add a use statement for Joomla\CMS\Helper\ModuleHelper.
2Replace every JModuleHelper with the short class name from that use line.
3Disable Behaviour – Backward Compatibility on a Joomla 5 staging site. If it fatals, this class is still in the code.

Also known as

JModuleHelper · Joomla\CMS\Helper\ModuleHelper · class alias · J prefix

Scan a ZIP for this Ask Infyways to fix it

JPAGINATION-CLASS-001

JPagination

JPagination class name

JPagination is a Joomla 3 global class. Joomla 4 still has an alias. Joomla 5 needs the Behaviour – Backward Compatibility plugin. Native Joomla 6 does not load that alias — you get Class "JPagination" not found.

JPagination → Joomla\CMS\Pagination\Pagination

Dies at Joomla 5 → 6

Dies at Joomla 5 → 6J3: Works nativelyJ4: Alias (old name still resolves)J6: Removed — fatalBC plugin: covers the class nameMechanical renameJoomla API

What you will see

Class "JPagination" not found
Class 'JPagination' not found
Failed to open stream: JPagination

Symptoms people search

white screen after disabling compatibility plugin · class not found on Joomla 6 · works on Joomla 5 until I turn off backward compatibility

Replace this code

Swap JPagination for Joomla\CMS\Pagination\Pagination.

Joomla 3

Remove or stop calling this

JPagination::getInstance();
// or new JPagination()

Joomla 4 / 6

Use this instead

use Joomla\CMS\Pagination\Pagination;

// Call the namespaced class. Do not keep the J prefix.

How to fix it

1Add a use statement for Joomla\CMS\Pagination\Pagination.
2Replace every JPagination with the short class name from that use line.
3Disable Behaviour – Backward Compatibility on a Joomla 5 staging site. If it fatals, this class is still in the code.

Also known as

JPagination · Joomla\CMS\Pagination\Pagination · class alias · J prefix

Scan a ZIP for this Ask Infyways to fix it

JPAGINATIONOBJECT-CLASS-001

JPaginationObject

JPaginationObject class name

JPaginationObject is a Joomla 3 global class. Joomla 4 still has an alias. Joomla 5 needs the Behaviour – Backward Compatibility plugin. Native Joomla 6 does not load that alias — you get Class "JPaginationObject" not found.

JPaginationObject → Joomla\CMS\Pagination\PaginationObject

Dies at Joomla 5 → 6

Dies at Joomla 5 → 6J3: Works nativelyJ4: Alias (old name still resolves)J6: Removed — fatalBC plugin: covers the class nameMechanical renameJoomla API

What you will see

Class "JPaginationObject" not found
Class 'JPaginationObject' not found
Failed to open stream: JPaginationObject

Symptoms people search

white screen after disabling compatibility plugin · class not found on Joomla 6 · works on Joomla 5 until I turn off backward compatibility

Replace this code

Swap JPaginationObject for Joomla\CMS\Pagination\PaginationObject.

Joomla 3

Remove or stop calling this

JPaginationObject::getInstance();
// or new JPaginationObject()

Joomla 4 / 6

Use this instead

use Joomla\CMS\Pagination\PaginationObject;

// Call the namespaced class. Do not keep the J prefix.

How to fix it

1Add a use statement for Joomla\CMS\Pagination\PaginationObject.
2Replace every JPaginationObject with the short class name from that use line.
3Disable Behaviour – Backward Compatibility on a Joomla 5 staging site. If it fatals, this class is still in the code.

Also known as

JPaginationObject · Joomla\CMS\Pagination\PaginationObject · class alias · J prefix

Scan a ZIP for this Ask Infyways to fix it

JUCM-CLASS-001

JUcmType

JUcmType class name

JUcmType is a Joomla 3 global class. Joomla 4 still has an alias. Joomla 5 needs the Behaviour – Backward Compatibility plugin. Native Joomla 6 does not load that alias — you get Class "JUcmType" not found.

JUcmType → Joomla\CMS\UCM\UCMType

Dies at Joomla 5 → 6

Dies at Joomla 5 → 6J3: Works nativelyJ4: Alias (old name still resolves)J6: Removed — fatalBC plugin: covers the class nameMechanical renameJoomla API

What you will see

Class "JUcmType" not found
Class 'JUcmType' not found
Failed to open stream: JUcmType

Symptoms people search

white screen after disabling compatibility plugin · class not found on Joomla 6 · works on Joomla 5 until I turn off backward compatibility

Replace this code

Swap JUcmType for Joomla\CMS\UCM\UCMType.

Joomla 3

Remove or stop calling this

JUcmType::getInstance();
// or new JUcmType()

Joomla 4 / 6

Use this instead

use Joomla\CMS\UCM\UCMType;

// Call the namespaced class. Do not keep the J prefix.

How to fix it

1Add a use statement for Joomla\CMS\UCM\UCMType.
2Replace every JUcmType with the short class name from that use line.
3Disable Behaviour – Backward Compatibility on a Joomla 5 staging site. If it fatals, this class is still in the code.

Also known as

JUcmType · Joomla\CMS\UCM\UCMType · class alias · J prefix · JUcm

Scan a ZIP for this Ask Infyways to fix it

JUCMBASE-CLASS-001

JUcmBase

JUcmBase class name

JUcmBase is a Joomla 3 global class. Joomla 4 still has an alias. Joomla 5 needs the Behaviour – Backward Compatibility plugin. Native Joomla 6 does not load that alias — you get Class "JUcmBase" not found.

JUcmBase → Joomla\CMS\UCM\UCMBase

Dies at Joomla 5 → 6

Dies at Joomla 5 → 6J3: Works nativelyJ4: Alias (old name still resolves)J6: Removed — fatalBC plugin: covers the class nameMechanical renameJoomla API

What you will see

Class "JUcmBase" not found
Class 'JUcmBase' not found
Failed to open stream: JUcmBase

Symptoms people search

white screen after disabling compatibility plugin · class not found on Joomla 6 · works on Joomla 5 until I turn off backward compatibility

Replace this code

Swap JUcmBase for Joomla\CMS\UCM\UCMBase.

Joomla 3

Remove or stop calling this

JUcmBase::getInstance();
// or new JUcmBase()

Joomla 4 / 6

Use this instead

use Joomla\CMS\UCM\UCMBase;

// Call the namespaced class. Do not keep the J prefix.

How to fix it

1Add a use statement for Joomla\CMS\UCM\UCMBase.
2Replace every JUcmBase with the short class name from that use line.
3Disable Behaviour – Backward Compatibility on a Joomla 5 staging site. If it fatals, this class is still in the code.

Also known as

JUcmBase · Joomla\CMS\UCM\UCMBase · class alias · J prefix

Scan a ZIP for this Ask Infyways to fix it

JUCMCONTENT-CLASS-001

JUcmContent

JUcmContent class name

JUcmContent is a Joomla 3 global class. Joomla 4 still has an alias. Joomla 5 needs the Behaviour – Backward Compatibility plugin. Native Joomla 6 does not load that alias — you get Class "JUcmContent" not found.

JUcmContent → Joomla\CMS\UCM\UCMContent

Dies at Joomla 5 → 6

Dies at Joomla 5 → 6J3: Works nativelyJ4: Alias (old name still resolves)J6: Removed — fatalBC plugin: covers the class nameMechanical renameJoomla API

What you will see

Class "JUcmContent" not found
Class 'JUcmContent' not found
Failed to open stream: JUcmContent

Symptoms people search

white screen after disabling compatibility plugin · class not found on Joomla 6 · works on Joomla 5 until I turn off backward compatibility

Replace this code

Swap JUcmContent for Joomla\CMS\UCM\UCMContent.

Joomla 3

Remove or stop calling this

JUcmContent::getInstance();
// or new JUcmContent()

Joomla 4 / 6

Use this instead

use Joomla\CMS\UCM\UCMContent;

// Call the namespaced class. Do not keep the J prefix.

How to fix it

1Add a use statement for Joomla\CMS\UCM\UCMContent.
2Replace every JUcmContent with the short class name from that use line.
3Disable Behaviour – Backward Compatibility on a Joomla 5 staging site. If it fatals, this class is still in the code.

Also known as

JUcmContent · Joomla\CMS\UCM\UCMContent · class alias · J prefix

Scan a ZIP for this Ask Infyways to fix it

JVIEWCATEGORIES-CLASS-001

JViewCategories

JViewCategories class name

JViewCategories is a Joomla 3 global class. Joomla 4 still has an alias. Joomla 5 needs the Behaviour – Backward Compatibility plugin. Native Joomla 6 does not load that alias — you get Class "JViewCategories" not found.

JViewCategories → Joomla\CMS\MVC\View\CategoriesView

Dies at Joomla 5 → 6

Dies at Joomla 5 → 6J3: Works nativelyJ4: Alias (old name still resolves)J6: Removed — fatalBC plugin: covers the class nameMechanical renameMVC

What you will see

Class "JViewCategories" not found
Class 'JViewCategories' not found
Failed to open stream: JViewCategories

Symptoms people search

white screen after disabling compatibility plugin · class not found on Joomla 6 · works on Joomla 5 until I turn off backward compatibility

Replace this code

Swap JViewCategories for Joomla\CMS\MVC\View\CategoriesView.

Joomla 3

Remove or stop calling this

JViewCategories::getInstance();
// or new JViewCategories()

Joomla 4 / 6

Use this instead

use Joomla\CMS\MVC\View\CategoriesView;

// Call the namespaced class. Do not keep the J prefix.

How to fix it

1Add a use statement for Joomla\CMS\MVC\View\CategoriesView.
2Replace every JViewCategories with the short class name from that use line.
3Disable Behaviour – Backward Compatibility on a Joomla 5 staging site. If it fatals, this class is still in the code.

Also known as

JViewCategories · Joomla\CMS\MVC\View\CategoriesView · class alias · J prefix

Scan a ZIP for this Ask Infyways to fix it

JVIEWCATEGORY-CLASS-001

JViewCategory

JViewCategory class name

JViewCategory is a Joomla 3 global class. Joomla 4 still has an alias. Joomla 5 needs the Behaviour – Backward Compatibility plugin. Native Joomla 6 does not load that alias — you get Class "JViewCategory" not found.

JViewCategory → Joomla\CMS\MVC\View\CategoryView

Dies at Joomla 5 → 6

Dies at Joomla 5 → 6J3: Works nativelyJ4: Alias (old name still resolves)J6: Removed — fatalBC plugin: covers the class nameMechanical renameMVC

What you will see

Class "JViewCategory" not found
Class 'JViewCategory' not found
Failed to open stream: JViewCategory

Symptoms people search

white screen after disabling compatibility plugin · class not found on Joomla 6 · works on Joomla 5 until I turn off backward compatibility

Replace this code

Swap JViewCategory for Joomla\CMS\MVC\View\CategoryView.

Joomla 3

Remove or stop calling this

JViewCategory::getInstance();
// or new JViewCategory()

Joomla 4 / 6

Use this instead

use Joomla\CMS\MVC\View\CategoryView;

// Call the namespaced class. Do not keep the J prefix.

How to fix it

1Add a use statement for Joomla\CMS\MVC\View\CategoryView.
2Replace every JViewCategory with the short class name from that use line.
3Disable Behaviour – Backward Compatibility on a Joomla 5 staging site. If it fatals, this class is still in the code.

Also known as

JViewCategory · Joomla\CMS\MVC\View\CategoryView · class alias · J prefix

Scan a ZIP for this Ask Infyways to fix it

JVIEWLEGACY-CLASS-001

JViewLegacy

JViewLegacy class name

JViewLegacy is a Joomla 3 global class. Joomla 4 still has an alias. Joomla 5 needs the Behaviour – Backward Compatibility plugin. Native Joomla 6 does not load that alias — you get Class "JViewLegacy" not found.

JViewLegacy → Joomla\CMS\MVC\View\HtmlView

Dies at Joomla 5 → 6

Dies at Joomla 5 → 6J3: Works nativelyJ4: Alias (old name still resolves)J6: Removed — fatalBC plugin: covers the class nameMechanical renameMVC

What you will see

Class "JViewLegacy" not found
Class 'JViewLegacy' not found
Failed to open stream: JViewLegacy

Symptoms people search

white screen after disabling compatibility plugin · class not found on Joomla 6 · works on Joomla 5 until I turn off backward compatibility

Replace this code

Swap JViewLegacy for Joomla\CMS\MVC\View\HtmlView.

Joomla 3

Remove or stop calling this

JViewLegacy::getInstance();
// or new JViewLegacy()

Joomla 4 / 6

Use this instead

use Joomla\CMS\MVC\View\HtmlView;

// Call the namespaced class. Do not keep the J prefix.

How to fix it

1Add a use statement for Joomla\CMS\MVC\View\HtmlView.
2Replace every JViewLegacy with the short class name from that use line.
3Disable Behaviour – Backward Compatibility on a Joomla 5 staging site. If it fatals, this class is still in the code.

Also known as

JViewLegacy · Joomla\CMS\MVC\View\HtmlView · class alias · J prefix

Scan a ZIP for this Ask Infyways to fix it

MVC-ASSIGNREF-001

$this->assignRef('item', $item)

assignRef() on views

assignRef was a PHP 4 leftover. It does nothing useful on Joomla 4+.

$this->assignRef('item', $item) → $this->item = $item

Dies at Joomla 3 → 4

Dies at Joomla 3 → 4J3: Works nativelyJ4: Removed — fatalJ6: Removed — fatalBC plugin: no — already dead on J4Mechanical renameMVC

What you will see

Call to undefined method ...::assignRef

Symptoms people search

view variables empty · assignRef

Replace this code

Swap $this->assignRef('item', $item) for $this->item = $item.

Joomla 3

Remove or stop calling this

$this->assignRef('items', $items);

Joomla 4 / 6

Use this instead

$this->items = $items;

How to fix it

1Assign properties directly.

Also known as

assignRef

Scan a ZIP for this Ask Infyways to fix it

MVC-GETERROR-001

$model->setError()

getError() / setError() on models and tables

setError/getError were the JError-era API. They linger in Joomla 3 components and fail silently or fatally once JError is gone.

$model->setError() → Exceptions

Dies at Joomla 3 → 4

Dies at Joomla 3 → 4J3: Works nativelyJ4: Removed — fatalJ6: Removed — fatalBC plugin: no — already dead on J4Architecture change — no auto-fixMVC

What you will see

Call to undefined method ...::getError()

Symptoms people search

save fails with no message · getError empty

Replace this code

Swap $model->setError() for Exceptions.

Joomla 3

Remove or stop calling this

if (!$table->store()) {
    $this->setError($table->getError());
    return false;
}

Joomla 4 / 6

Use this instead

try {
    $table->store();
} catch (\RuntimeException $e) {
    $this->setError($e->getMessage()); // better: throw
    throw $e;
}

How to fix it

1Throw on failure.
2Stop returning false plus getError() as the only signal.

Also known as

getError · setError

There is no 1:1 swap for this one. The architecture changed. If you cannot rewrite it, Infyways can.

Scan a ZIP for this Ask Infyways to fix it

MVC-GETINSTANCE-001

JModelLegacy::getInstance()

getInstance() on MVC classes

String getInstance on models/controllers/views is deprecated. MVC Factory resolves namespaced classes.

JModelLegacy::getInstance() → $this->getModel() / MVCFactory

Dies at Joomla 5 → 6

Dies at Joomla 5 → 6J3: Works nativelyJ4: Deprecated — do not shipJ6: Deprecated — do not shipBC plugin: not applicablePatch possible — review itMVC

What you will see

Model class not found

Symptoms people search

getInstance model · cannot load model after namespace

Replace this code

Swap JModelLegacy::getInstance() for $this->getModel() / MVCFactory.

Joomla 3

Remove or stop calling this

$model = JModelLegacy::getInstance('Courses', 'LmsModel');

Joomla 4 / 6

Use this instead

$model = $this->getModel('Courses');

How to fix it

1Use $this->getModel() in controllers.
2Register the MVC factory in services/provider.php.

Also known as

JModelLegacy::getInstance · JControllerLegacy::getInstance

Scan a ZIP for this Ask Infyways to fix it

MVC-NEW-J3-001

Joomla\CMS\MVC (J3 experimental)

Experimental Joomla 3 “new MVC” namespace

Joomla 3 shipped an experimental MVC that Joomla 4 deleted. If you followed those J3 sample classes, they are gone.

Joomla\CMS\MVC (J3 experimental) → Original MVC: HtmlView, ListModel, BaseController

Dies at Joomla 3 → 4

Dies at Joomla 3 → 4J3: Works nativelyJ4: Removed — fatalJ6: Removed — fatalBC plugin: no — already dead on J4Architecture change — no auto-fixMVC

What you will see

Class ... not found in experimental MVC

Symptoms people search

J3 new MVC tutorial code 500

Replace this code

Swap Joomla\CMS\MVC (J3 experimental) for Original MVC: HtmlView, ListModel, BaseController.

Joomla 3

Remove or stop calling this

use Joomla\CMS\MVC\View\HtmlView as Experimental;

Joomla 4 / 6

Use this instead

Use the Joomla 4 MVC that came from the old legacy MVC, not the J3 experimental split. HtmlView / ListModel / FormController.

How to fix it

1Port to the current namespaced MVC from JModelLegacy/JViewLegacy lineage.

Also known as

experimental MVC · Joomla 3 new MVC

There is no 1:1 swap for this one. The architecture changed. If you cannot rewrite it, Infyways can.

Scan a ZIP for this Ask Infyways to fix it