In order to run Windows commands via PHP functions such as open_proc(), apparently one has to grant read/execute permissions to the account under which IIS is running (usually IUSR_<servername>) on C:\WINDOWS\System32\cmd.exe. Be sure to do this for web apps that rely on external commands.
This of course took me an eternity to figure out. I was only able to piece together WebSVN‘s bizarre Windows mis-behavior after scouring through the remnants of forum posts limboed in Google cache. PHP.net of course has no proper details on this, though I do now better understand what proc_open‘s obscure and undocumented bypass_shell parameter might be about.
Ah yes, PHP on Windows. Obscure and irritating.
Kind of like me. Not that that makes it any better.
Note: If you are using Apache, instead of IIS, the same still applies. Moreover, I was having similar problems with Appache / PHP commands not running Windows based commands, but then I read this post, adjusted the user at the “services.msc” level for the “Apache” service and BINGO!!!
Thanks for the obscure, yet insightful post.
-mmuras