To solve the issue, find the php_openssl.dll file, for me it was in the very same directory of the compilation output:
C:\php-sdk\bin\phpdev\vc14\x64\php-7.0.13-src\x64\Release_TS
因此,只需将扩展名所在的目录添加到 php.ini:
Open your php.ini file and remove the semicolon from this line (you might want to uncomment other things as well but this line is the only one necessary for Composer)
;extension=php_openssl.dll
That should be all you need to do. The Composer installer should do everything else you need from here.