But then again, wouldn't that prevent PHP from being run as well, since it is server-side?
From http://en.wikipedia.org/wiki/Opera_Mini#JavaScript_support:
Opera Mini has limited support for JavaScript. Before the page is sent to the mobile device, its onLoad events are fired and all scripts are allowed a maximum of two seconds to execute. The setInterval and setTimeout functions are disabled, so scripts designed to wait a certain amount of time before executing will not execute at all. After the scripts have finished or the timeout is reached, all scripts are stopped and the page is compressed and sent to the mobile device. Once on the device, only a handful of events are allowed to trigger scripts: onUnload, onSubmit, onChange, onClick
Unfortunately, it also means it's a completely crippled browser. Why anyone would WANT to use it instead of something fully functional (like Safari) is beyond me. The days of squinting at tiny mobile versions of websites on a 2x1 cell phone screen are behind us, and good riddance. It would appear that Opera Mini is already obsolete on the iPhone due to its very architecture.
Granted neither of these cases are exactly everyday occurrences for your average iPhone owner, but for those people who find themselves in the above situation, having something like Opera mini to fall back on would be very handy.