PHP on IIS doesn’t load sqlsrv extension

I'm trying to put together a page that can submit data from a form to an MSSQL database via PHP. I've got PHP installed successfully (phpinfo() runs fine even on a remote computer) but it will not load the sqlsrv extension. I know that I'm editing the right php.ini file because I have another extension added (wincache) and it is loading fine, confirmed with both phpinfo() and get_loaded_extensions().

The logs aren't telling me anything. PHP Manager on IIS is telling me that the sqlsrv extension files are enabled. I've restarted the website, the server, and the computer, and nothing's working.

I'm using PHP 7.1.1 on a Windows 7 Ultimate machine. It's running in x64 mode, Non-Thread Safe. I've made sure that the extension files I enabled are the x64, non-thread-safe ones. I don't know what else to check or what more info I need to provide.

EDIT: I ran php-cgi.exe as this page suggested, and it came out with the error mesages:

[31-Mar-2017 22:38:12 UTC] PHP Warning:  PHP Startup: Unable to load dynamic library 'C:\Program Files\iis express\PHP\v7.1\ext\php_sqlsrv_7_nts_x64.dll' - The specified procedure could not be found.
 in Unknown on line 0
[31-Mar-2017 22:38:17 UTC] PHP Warning:  PHP Startup: Unable to load dynamic library 'C:\Program Files\iis express\PHP\v7.1\ext\php_pdo_sqlsrv_7_nts_x64.dll' - The specified procedure could not be found.
 in Unknown on line 0

Does this mean that the problem is in the extension DLLs themselves? How would I even go about fixing that?