PHP 7.1 Installation Tutorial

First, http://php.net/downloads.php#v7.1.9

Iis
If you are using PHP fastcgi IIS, you should use a non-thread-safe (NTS) version of PHP.

Apache
Please use Apache build provided by Apache Lounge. They offer the VC9,VC11 and VC14 versions of Apache for x86 and x64. We use their binaries to build Apache SAPI.

If you use PHP as a apache.org (not recommended) Apache module, you need to use the old visual Studio 6 compiled version of PHP VC6. Do not use apache.org binaries for VC9 + version of PHP.

With Apache, you must use the thread Safe (TS) version of PHP.

PHP 7.1 Installation Tutorial