Testing mode is important before deployment of the php 8 version. Plenty of bugs are happening if you are using upgrading your PHP version software and hardware version must go together to get all functionality of your website healthy and good. Back-up first before you make some updates. New version in PHP is moving to php 8 but still on test mode. No not use in your productive site. Always match the software you are using in your Linux server otherwise bugs and error will occur and damage the syntax of your programs.
The PHP team is pleased to announce the fifth testing release of PHP 8.0.0, Beta 2. This continues the PHP 8.0 release cycle, the rough outline of which is specified in the PHP Wiki.
CSS for website:
https://modernizr.com/resources
Booking system:
https://www.classroombookings.com/pricing/
Resources for editor:
https://alternativeto.net/software/textmate/?platform=windows