If you integrate PHP via FastCGI on IIS 7.5, every script is aborted by default after 600 seconds (i.e. 10 minutes). Changing the well-known variable "max_execution_time" in php.ini has no influence on this; you must (also) adjust the FastCGI settings. For this purpose, IIS offers a convenient interface for managing the relevant variables.
To do this, open the Internet Information Services (IIS) Manager, click on the appropriate server and then on FastCGI Settings:
After double-clicking on php-cgi.exe you will find the relevant options "Activity timeout" and "Request timeout" under "Process model":
These two values can now be increased to 7200 each to extend the timeout to 2 hours.