Letter "a" at the beginning of every request using built in PHP server with laravel causing Unexpected EOF

So, yesterday all was fine but today all every time a load a page a letter a briefly appears in the top left. Also, I use InterventionImage with some of my images, so I am not directly loading an image file and this a has broken those (http://ift.tt/1RyJrDy). But I also noticed that this mysterious a also appears at the begging of composer commands (http://ift.tt/1UCZoie). When I load one of these images in a new tab I get the following error: Invalid request (Unexpected EOF) I am totally stumped and would appreciate any help at all! Thanks!

via Chebli Mohamed