I'm having this error in Joomla for some reason:

Call to undefined method Joomla\CMS\Application\AdministratorApplication::isSite()

image of error

I see other posts with this error, but I suppose they are using the Joomla app or installed on local files. In my class exercise, it is obligatory to use the web implementation of Joomla so I don't know how to apply the advice in other answers or if they even work.

Continuing with my case, I can't do anything. I can't enter the website, log out, see the administrator, edit my account, etc.

I am using Joomla 3.1.

  • Welcome to JSE, cent3fs9. I have edited your question to try to improve the English. If I have damaged any part of your question, please edit the question and make appropriate changes. Since you are new here, please take our tour and read How to Ask. I don't know that volunteers have enough information to help yet. If there are more clues about how you set up your Joomla site, please edit them into your question body. Other contributes may ask for more specific details before they are able to answer. Mar 29, 2022 at 10:57
  • Please switch error repoting to development in your Global Configuration, so that you know which file/line is triggering the error
    – Lodder
    Mar 30, 2022 at 10:16

1 Answer 1


Your Joomla version is 3.1. Method isSite() is found here: libraries/src/Application/CMSApplication.php line 733 since joomla 3.2 and is marked as deprecated.

 * Is site interface?
 * @return  boolean  True if this application is site.
 * @since       3.2
 * @deprecated  4.0 Use isClient('site') instead.
public function isSite()

May be you're using an extension that is too new for your Joomla version.

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