Add phpdocumentor

[at15]

add http://phpdoc.org/ to generate doc for php source. and may put it in gh branch.

• generate documentation
• use travis-ci to publish it to gh-pages branch http://benlimmer.com/2013/12/26/automatically-publish-javadoc-to-gh-pages-with-travis-ci/

[at15]

close due to age