Atom will be discontinued at the end of 2022: https://github.blog/2022-06-08-sunsetting-atom/
Enjoy productive PHP and web development with PhpStorm. Take advantage of deep code understanding, top-notch coding assistance, and support for all major tools and frameworks.
AWS Cloud9 is a code editor and development environment built with browser technology yet with the power of a desktop IDE. It's available both as an online service and as a locally hosted platform.
PythonAnywhere is a Python development and hosting environment that displays in your web browser and runs on cloud servers. The servers are already set up with everything you need: hundreds of useful Python packages and web frameworks are supported out of the box.
Codiad is an open source, web-based, cloud IDE and code editor with minimal footprint and requirementsDiscontinued
"Given its age and number of viable alternatives now available, Codiad is no longer under active maintenance by core contributors."https://github.com/Codiad/Codiad/commit/19c9223d70ca0eb164b6891b6e1350c75a62e8f2
Judge0 IDE is a free and open-source online code editor that allows you to write and execute code from a rich set of languages. It's perfect for anybody who just wants to quickly write and run some code without opening a full-featured IDE on their computer.