Go to http://yourhost.yourdomain/yourwikidir/admin.php.
ZIP Snapshot : contains only the latest versions
ZIP Dump : contains all archived versions
These links lead to zip files, generated on the fly, which contain the most recent versions of all pages in the PhpWiki. The pages are stored, one per file, as MIME (RFC2045) e-mail (RFC822) messages, with the content type application/x-phpwiki for the snapshot and content type multipart/mixed for the dump. In the latter case, there is one subpart (with type application/x-phpwiki) for each version of the page (in chronological order). The message body contains the page text, while the page meta-data is included as parameters in the Content-Type: header field.
Here you can load or dump pages of your Wiki into a directory of your choice.
Pages will be written out as "serialized" strings of a PHP associative array, meaning they will not be human readable. If the directory does not exist PhpWiki will try to create one for you. Ensure that your server has write permissions to the directory!
If you have dumped a set of pages from PhpWiki, you can reload them here. Note that pages in your database will be overwritten; thus, if you dumped your FrontPage when you load it from this form it will overwrite the one in your database now. If you want to be selective just delete the pages from the directory you don't want to load.