This plugin, although not updated for years, I still found it to be the best solution for writing HTML/PHP code into posts/pages/widgets. I have tried many other solutions, but none stands out as this. The only reasons I haven't rated it 5 stars are:
- It has not been updated for ages (although it works), and,
- Because of the annoying alert that appears at top of all admin pages. This alert should have an option to turn off globally and not for each profile individually.