错误：如果发出else else语句，则无法设置标头

Although this seems to be a very common question - based on what I've read I can't see the problem with my code. Below you will see that I'm using return if the condition is satisfied so I would think that it wouldn't try and set headers with my else condition. Please take a look and let me know if there's something I'm missing here:Although this seems to be a very common questio