Functions.php error

Hi, in the latest versions of Betheme there is an error Undefined array key "jsclass". This error appears every time I save changes to the page. As I found out, this error is caused by the fact that I added a function to disable Gutenberg in the child theme:

add_filter( 'use_block_editor_for_post', '__return_false' );

Can this be fixed or do I have to replace the feature on all websites with a plugin?

Best regards,



  • For example, this website:

    But the frontend is perfectly fine.

  • Hi,

    Sorry, but we do not provide help with child theme file customization.

    However, in Theme options -> Global -> Advanced, there is already an option to hide the WordPress Editor.

    Best regards

  • Hi Phil, thanks for your reply. Unfortunately, completely hiding the WordPress Editor does not solve anything for me, because then, for example, it is necessary to insert posts via the builder.

    For me, it is only about suppressing Gutenberg and thus having a basic (classic) version of the WordPress Editor.

    I solved this by adding a filter in functions.php. This is a standard feature in WP, so I don't consider it a custom modification. This worked without problems until version 27.2.10.

    Best regards,


  • As I know there is a plugin called Classic Editor that changes Gutenberg to the old Classic editor.

    Unfortunately, as I mentioned, I cannot help with modifications to the child theme.

    Best regards

  • Hi Phil, thanks for your reply.

    If I use the Classic Editor plugin or the Disable Gutenberg plugin or the WPCode plugin, I always get the same error message.

    As far as I know, all of these solutions use a command

    add_filter( 'use_block_editor_for_post', '__return_false' );

    So in my opinion it is a collision of recent versions of Betheme with this standard WordPress feature. The problem is not only about child theme customization.

    Best regards,


  • For confirmation, we checked this filter in our environment, and it works properly.

    Please send us the WordPress dashboard and FTP access privately through the contact form, which is on the right side at and we will check what might be the reason.


    Please attach a link to this forum discussion.

    Sending incorrect or incomplete data will result in a longer response time.

    Therefore, please ensure that the data you send are complete and correct.


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