Hi, I`m trying to work out how to migrate a Drupal 7 site to Backdrop. At the moment I haven't migrated anything, I'm just looking at everything. It seems one of the major tasks is the theme, so at the moment I just have a standard Backdrop install and I'm trying to get my theme to work.

I installed the Drupal 7 Compatible theme in order to use my Drupal 7 theme, enabled the Drupal7 Compatible theme and then set my Drupal Site as the default site. The background colour is the colour of my Drupal 7 theme and the Site title appears, but the rest of the screen is blank. Underneath The site title is the following message:


[] operator not supported for strings


Also the Admin menus at the very top of the screen disappear. They don't when the standard themes are enabled.

Does anyone know how I can solve this?


Many thanks in advance


Hi, acp963, and welcome to the Backdrop forum!

Yes, theme conversion is a big task. I don't have much experience with the Drupal 7 Compatible theme, but the little I've seen indicates this is not an "out of the box" solution. 

I'd suggest you take a look at the steps to convert themes outlined here. I think that may provide a doable way to make your theme work in Backdrop without using or tinkering with Drupal 7 Compatible. 

Thank you for your answer. I've already looked at the link you provided quite intensively, and also tried converting the Drupal 7 theme to Backdrop. I came unstuck with the conversion of CSS selectors from IDs to classes. I thought the whole idea of the Drupal 7 Compatible theme is to make it easier to use a Drupal theme in Backdrop? Is there a way to get more information about the error?




I'm not familiar with the Drupal 7 Compatible theme, so I can't help you with that. You may want to post in the issue queue for that theme.

Can you post full information about the error you are getting, such as the line and file/function where it's happening?  

Thank you for your reply. There is no other information provided. Is there a way to set Backdrop to provide more verbose error messaging?

Are you doing this locally? What environment do you use? ddev, lando, MAMP, etc?

Check to see if you have a php_error.log file that may contain more info.

Here's a hunch: are you trying implode(' ', $classes) somewhere in your template file? If you have enabled Drupal 7 Compatible AND you are also trying to flatten the classes array, this may be causing the error. AFAIK Drupal 7 Compatible will flatten that array for you, you don't need to do it again.

Yes, locally using Xampp, When I tried the Drupal 7 Compatible theme, I used an unchanged version of my Drupal 7 theme, except for the required changes noted in the ReadMe document of the Drupal7 Compatible theme.

Actually I just tried making the 'Drupal 7 Compatible theme' the default theme and I get the same error:


[] operator not supported for strings


Does that mean  the error must lie with that theme?