If you have a clean install of PHP 7.0 or today’s release of PHP 7.0.8 running on a Windows 2008 – Windows 2012 R2 IIS 7.5 or IIS 8.0 and you are receiving a 500 internal server error, the first thing you should verify is that you have installed Visual C++ Redistributable for Visual Studio 2015. Download is available here. If that doesn’t work, make sure this is commented out in your php.ini  ;open_basedir =

If you are running WordPress, many plugins, themes, etc will not work yet with PHP 7.0 so you need to test everything out with a basic php file, or a clean install of WordPress with no plugins, paid themes, etc.

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