If you are using theme_get_settings, such as: $value = trim(theme_get_setting('my_setting')); Then in your code editor you will also be seeing undefined  function 'theme_get_setting'.  This function has been deprecated for some time.   Instead, you need to use Passing the theme.manager and theme.initialization services to theme_handler constructor as optional parameters is deprecated. These parameters are also mandatory. $theme_handler = \Drupal::service('theme_handler');Get...

As outlined in an earlier article composer php version, when installing the latest version of Drupal the Plesk version and the server version can be different.  In plesk, the version of PHP is 7.3.18, whereas, on the Centos server a check through Terminal (php -v) shows PHP 7.1.33 (cli). When attempting to install Drupal 9 through composer, the following errors will be shown: Problem 1 - drupal/core-composer-scaffold 9.1.x-dev requires php >=7.3.0 -> your PHP version...