I installed the PHP Server extension for VS Code and added two lines to settings.json:
"php.validate.executablePath": "С://php-server//php.exe",
"phpserver.phpPath": "С://php-server//php.exe"
I inserted these lines before the closing bracket ("}") and added a comma on the previous to last line.
I restarted VS Code and got the message:
Unable to validate because h:\web\php\с:\php-server\php.exe is not a valid PHP executable. Use the php.validate.executablePath parameter to configure the PHP executable.
No matter what I tried, it still looks for php.exe on the disk with the device letter "h".
"С:\\php-server\\php.exe". This may not yet change the outcome but to make your question more clear you should show both tries. Double check it, then edit with the update @Andrianovi.