Hi,
please have a look at this bug report regarding the PHP ignore_user_abort setting having no effect on IIS with FastCGI.
"Bug #60586: ignore_user_abort=true has no effect on IIS with FastCGI"
https://bugs.php.net/bug.php?id=60586
I'm wondering if this is a PHP issue at all or a Microsoft/IIS one.
Best regards
Lars