If PHP has any problems running, then a suitable error message will be displayed which will give you a clue as to what needs to be done next.
This error message means that PHP failed to output anything at all. To get to see a sensible error message, from the command line, change to the directory containing the PHP executable (php.exe on Windows) and run php -i. If PHP has any problems running, then a suitable error message will be displayed which will give you a clue as to what needs to be done next. If you get a screen full of html codes (the output of the phpinfo() function) then PHP is working.