standards/php.md - Add a TLDR example

Created by: totten

To see actual examples of the coding style, you need to skim multiple blurbs and click multiple links, and the eventual page shows very isolated examples.

This revision adds a brief example so that a new contributor can get a general sense of the layout immediately.

(Note: It's not possible for a brief example to show every edge-case, and we shouldn't try -- that's why the commit also emphasizes the link into the relevant examples from d.o docs.)