Something went wrong when the server tried to run PHP. 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, and your problem may be related to your server configuration which you should double check.
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