Windows users:
Note: Note to Win32 Users In order to enable this module on a Windows environment, libeay32.dll and ssleay32.dll, or, as of OpenSSL 1.1 libcrypto-.dll and libssl-.dll, must be present in your PATH. Also libssh2.dll must be present in your PATH. You don't need libcurl.dll from the cURL site.
https://www.php.net/manual/en/curl.installation.php
Add your C:\wamp\bin\php\php7.1.15 to your PATH
Restart all services