IIS 7 and Above
PHP Configuration Issue
Re: PHP Configuration Issue
Jun 11, 2013 06:53 PM|szarkos|LINK
This sounds like it could be an execution timeout issue. Can you check how long it takes from when you access the page (or click "submit" or whatnot) to when you receive the 500 error. If the timing is consistent that usually suggests a timeout issue.
I would recommend checking the following:
IIS has other timeouts as well (such as ConnectionTimeout which is set to 120 seconds by default), but if your uploads work with ASP and not with PHP that seems less likely to be the issue.