The PHP manual is available not only in various formats, but also in various languages. The text of the manual is first written in English, then teams of people across the world take care of translating it to their native languages. If a translation for a specified function or chapter has not yet been made, the manual's build system falls back to the English version of it.
People involved in the translations start from the XML source code available from » https://svn.php.net/viewvc/ and from it they translate to their mother language. They do not use the generated versions (like HTML or plain text) as it's the build system that takes care of the conversions from XML to human readable formats.
To help translate the documentation, please get in touch with the translation/documentation team by subscribing to the phpdoc mailing list: send an empty mail to » [email protected]. The mailing list address is [email protected]. State in the message an interest in translating the manual and someone will reply with feedback on moving forward by helping start a new language translation, or by contacting the existing team for the desired language.
At the moment the manual is available, partly or not, in over 10 languages.
They may all be downloaded here: » https://www.php.net/docs.php.