BC5-DISABLE-TEST-001

plg_behaviour_compat

Site dies when you disable Behaviour – Backward Compatibility

There are two plugins. Behaviour – Backward Compatibility (no number) restores JFactory, JText, JHtml, and hundreds of J* names on Joomla 5. You MUST disable it before Joomla 6. Behaviour – Backward Compatibility 6 is a different plugin and does not restore JRequest or JFactory. If disabling the first plugin whitescreens the site, you are not Joomla 6 ready.

plg_behaviour_compat → Rewrite J* classes so BC5 can stay off, then upgrade to Joomla 6

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

What you will see

  • Class "JFactory" not found
  • Class "JText" not found
  • Class "JHtml" not found

Symptoms people search

white screen after disabling compatibility plugin · cannot upgrade to Joomla 6 · plugin required for site to load · backward compatibility

Replace this code

Swap plg_behaviour_compat for Rewrite J* classes so BC5 can stay off, then upgrade to Joomla 6.

Joomla 3

Remove or stop calling this

// Joomla 5 with plugin enabled — site “works”
$app = JFactory::getApplication();

Joomla 4 / 6

Use this instead

use Joomla\CMS\Factory;
$app = Factory::getApplication();
// Then disable the plugin on staging. It must stay off to upgrade to Joomla 6.

How to fix it

  1. 1On Joomla 5.4 staging: System → Plugins → disable Behaviour – Backward Compatibility (no number).
  2. 2Note every Class "J…" not found error. Those are this reference.
  3. 3Fix them, then retry. Only then run the Joomla 6 update.
  4. 4Do not confuse it with Backward Compatibility 6 — that one does not bring J* names back.

Also known as

Behaviour - Backward Compatibility · plg_behaviour_compat · BC plugin · compat plugin · Backward Compatibility 6

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