I have a development environment based in docker.
Everytime that I open VSCode I get this message:
Cannot validate since no PHP executable is set.
My case, I'm using Laragon, so you should search where is your php.exe.
By VSCode just add.
"php.executablePath": "C:\\laragon\\bin\\php\\php-7.2.19-Win32-VC15-x64\\php.exe"
on settings.json.