Ensure PHP track is ready for v2 launch about php HOT 1 CLOSED

Things that can already be checked off:

The track has a page on the v2 site: https://v2.exercism.io/tracks/php
The code example gives a good taste of the language and fits within the boundaries of the background image
Exercises have rough estimates of difficulty

Things that need to be completed:

• Add a blurb to config.json
• Change the about section slightly to avoid using lots of technical terms, and aim for sounding friendly & colloquial (such as removing "dynamic inclusions" and "headless parsing")
• Set ~8 exercises as core in config.json, and add unlocked_by to other non-core exercises
• Some exercises (15+) are missing topics

I've added a pull request to add auto_approve to the first exercise (#207)

from php.