I use emacs as IDE, and wanted to have direct feedback about the validity of my .php files when writing them. The most easy way was to add a save hook that runs PHP_CodeSniffer - but the results should be displayed in a nice, unobtrusive way. phpcs has multiple reporting modes - xml, checkstyle, csv etc. - but nothing for the desktop. I thought that notify-send would be the right fit since it is able to display pretty popup messages without getting in the way.

He also includes the details on his original objective - including it in a "on save" hook as well as providing it in a keystroke shortcut, making checking his code even easier.