Ian Selby, working for a startup and building a lot of code up from scratch came across a problem - the upload of pretty large files via PHP:

I have found myself in a position where I am writing scripts that may need to upload fairly large files. My scripts were timing out, and I couldn't seem to figure out why. For the unitiated, there are some standard things that you usually do to both your php.ini and in your script in this situation [...] However, it turns out there are some other php.ini config variables that you may need to look at.

The "usual suspects" list includes changing the max_upload_size value and adjusting the script timeout. The other settings he mentions, though, are things like memory_limit, post_max_size and max_input_time to help increase the default times that PHP uses on most page executions.