$_FILES is a global multi-dimensional array defined by php. If you would like to see the contents of the array you can use the print_r() function.
PHP Code:
print_r($_FILES['new_image']);
To access an element in the array, you need to ask for its exact index. For example
PHP Code:
echo $_FILES['new_image']['name'];
will echo the name of the file. See here for more information:
PHP: Handling file uploads - Manual
I've written a upload class that you can modify if you would like:
PHP: Upload Class