Sorry to be jumping to this discussion so late!
PHP support
We will not be adding PHP support to Bootstrap Studio. This is because PHP generates HTML, and there is no way to make this work with a visual drag and drop builder. The HTML of your page needs to come from one place - either it’s generated from the app when you drag and drop components, or from PHP when code is executed. If an editor were to have both, this would come with significant limitations, and in the end it won’t be good at either visual nor PHP editing.
It would be nice to have, of course, but it would ruin Bootstrap Studio as a visual editor.
Running JS in the app window
This is another thing we won’t be doing. JS will need to run in the same process as the Bootstrap Studio window. Electron can isolate the code, but a single while(1){} loop can block the entire thread and cause the application to freeze. Even if this is somehow solved, you still need to see JS errors, have a step by step debugger, write code in the console… Just use the browser preview.