The newest stable version of the php5 port is located here: http://pubsvn.ez.no/nextgen_php5/stable/3.9/
This 3.9 version is 3.9.2 currently.
1. extract the version you want into a new host
2. copy the var content (but delete the content of the cache folders )
3. copy setting, your design and extensions
4. if you have copied any extensions search true the php files in them for '&=' and 'function &FunctionName' and remove '&'
5. make a copy of the db and setup the new install with the new db copy 6. do the upgrade scripts if its a different version.
Hopefully your new php5 site is up now :) Notice: #4: you only need to remove the once that return objects.