While there are cloud-based IDEs, doing PHP development in a cloud IDE is still far from turnkey.
Source: When it comes to cloud-based PHP development, the sticking point is the debugger | ZDNet
As this article points out, developing and especially debugging code with a cloud-based IDE still is not optimal.
I was tempted to try out a Pixelbook for programming, but I will stick with my MacBook Pro in which I can run Windows (or even Linux) in a virtual machine.
CodeAnywhere and other cloud-based IDEs are more suited for doing quick edits or doing an SSH session into your site, but not full development.
Eventually we’ll get to that point, but not at this time.