I've just updated one of its pages editing php code by windows notepad, and it really was a busy task since the code isn't even displayed in column but it's laid out on long rows

I agreed to update such a site since I was thinking about html pages.
I was thinking I can quite easily handle text and images with the right software almost like using an advanced word processor...
I don't know if it's the same with php; I lack any suitable software anyway...
Any suggestion?