Array and string offset access syntax with curly braces is no longer supported in PHP 7.4+

[andrewl64]

WordPress v5.7.1 | Unyson v2.7.24 | PHP v8.0.5

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From PHP 7.4+ (technically it was to be deprecated in PHP 5.1), array and string offset access syntax with curly braces has been deprecated. However, the Unyson backups extension seems to still use curly braces in class-fw-ext-backups-task-type-db-export.php, class-fw-ext-backups-task-type-db-restore.php, class-fw-ext-backups-task-type-files-export.php and class-fw-ext-backups-task-type-files-restore.php.

This seems to result in an "ajax errors" warning causing the backup to fail with the following errors returned when trying to Create Full Backup/Create Content Backup:

PHP message: PHP Fatal error:  Array and string offset access syntax with curly braces is no longer supported in /home/example/public_html/wp-content/plugins/unyson/framework/extensions/backups/includes/module/tasks/type/class-fw-ext-backups-task-type-db-export.php on line XXX" while reading response header from upstream....

PHP message: PHP Fatal error:  Array and string offset access syntax with curly braces is no longer supported in /home/example/public_html/wp-content/plugins/unyson/framework/extensions/backups/includes/module/tasks/type/class-fw-ext-backups-task-type-db-restore.php on line XXX" while reading response header from upstream....

PHP message: PHP Fatal error:  Array and string offset access syntax with curly braces is no longer supported in /home/example/public_html/wp-content/plugins/unyson/framework/extensions/backups/includes/module/tasks/type/class-fw-ext-backups-task-type-files-export.php on line XXX" while reading response header from upstream....

PHP message: PHP Fatal error:  Array and string offset access syntax with curly braces is no longer supported in /home/example/public_html/wp-content/plugins/unyson/framework/extensions/backups/includes/module/tasks/type/class-fw-ext-backups-task-type-files-restore.php on line XXX" while reading response header from upstream....