Contributing to php doc-en

Hi PHP doc contributors,

I am Roy, a software engineer living in the Netherlands.
I am interested in helping out with the PHP documentation and right now I
am working my way through the English documentation (see how it's
structured, build etc..).

The two repositories I have checked out:
- doc-base => php/doc-base
- doc-en => php/en

Running 'php doc-base/configure.php --enable-xml-details
--disable-libxml-check --redirect-stderr-to-stdout --with-lang=en' results
in
All good. Saving .manual.xml... done.
All you have to do now is run 'phd -d
/mnt/projects/php/doc-base/.manual.xml'

However, phd is not present on my system and I couldn't find anything about
it.

Can anyone help out by pointing me in the right direction?

Best regards,
Roy