Process DLLs as PHP

Hi, I have a system that legacy clients need to connect to, and they are expecting to talk to an ISAPI DLL. I'm rewriting this server in PHP but am having difficulty getting DLL files to be processed as if they were PHP files.

Under that server, Services, Configure Website, Edit Directives, I added:

AddType application/x-httpd-php .dll AddHandler fcgid-script .dll FCGIWrapper (domain removed)/php7.2.fcgi .dll

But going to a URL which ends in DLL still just results in the file being downloaded. What am I missing?