The soon to be released iOS 6 gives a subtle hint about the iPhone’s 5 screen size.  The website 9to5Mac has found that an application called the iOS simulator has been tweaked in iOS 6, which is used to build iOS apps. What they found was that they were able to expand the screen resolution to match the resolution that of the rumoured iPhone 5 screen size which has a resolution of 640 x 1136 also when the image was expanded to that size an extra row of apps was also automatically added onto the home screen. In iOS 5.1 when the same resolution was applied it just made the four rows of home screen apps appear to further spread out across the larger screen space. 

However it cannot be concluded that this is evidence that confirms that apple is planning to release an iPhone 5 with a larger display. It could just be an indication that apple are simply testing a prototype screen that they never plan to release. Until apple finally make an an announcement which is rumoured to be on September the 12th,  we will not know for sure.