improved php doc

* added php image
* modified intro message
* added missing lib
* split drivers between environment usage
* added apps links using php and neo4j
Hrm, looks like a previously-existing typo! "these drivers" not "tohese drivers", and should all be on one line:

Members of the PHP community have invested a lot of time and love to develop all these drivers, so if you use them please provide feedback to the authors.