First, before you can actually make documentation changes, you need write access to the » svn.php.net SVN repository. You can always checkout a module anonymously, but you can not commit changes unless you have an account. If you only would like to check files out, you can simply check out the sources anonymously. See the » php.net SVN page for more information.
Also note, that if you have a SVN account on our server, you may have no write access to the phpdoc and/or to your translation's module. The Karma system controls who have access to what module, so if you have a SVN account but have no Karma to write, please ask for Karma at » firstname.lastname@example.org. Note, that who has Karma to write to the PHP source tree, has Karma to phpdoc as well.
Obtaining a SVN account at php.net isn't difficult, but you need to do two things:
Both of the above steps and other information about SVN accounts at svn.php.net can be found on the same page as the request form, » http://www.php.net/svn-php. Note that this it not an automated process. If you receive no response after days, do not hesitate to post a mail to the PHP Group and ask for consideration.