PHP5 and Tikiwiki are working nicely on gentoo without much hassle. Only session support had to be compiled in.

On gentoo I used the following USE flags for mod_php-5.0.2 with apache2:
-adabas +apache2 -bcmath +berkdb* -birdstep -bzlib -calendar -cdb -cpdflib +crypt -ctype -curl -curlwrappers -db2 +dba -dbase -dbm -dbmaker -dbx -debug -dio -empress -empress-bcs -esoob -exif -fam -fdftk -filepro -flatfile -frontbase -ftp +gd -gd-external +gdbm -gmp -hyperwave-api -iconv +imap -informix -ingres -inifile -interbase -iodbc +jpeg -ldap -libedit -mcve +memlimit -mhash -mime -ming -mnogosearch -msession -msql -mssql +mysql -mysqli +ncurses -nis +nls -oci8 -odbc -oracle7 -ovrimos -pcntl -pcre -pfpro +png -posix +postgres -qdbm +readline -recode -sapdb -sasl +session -shared -sharedmem -simplexml +snmp -soap +sockets -solid +spell -spl -sqlite +ssl -sybase -sybase-ct -sysvipc -tidy +tiff -tokenizer +truetype -wddx +xml2 -xmlrpc -xpm -xsl +zlib

Image Galleries and File Uploads work fine with mod_php 5.0.2 on gentoo with the above USE flags

turck-mmcache is a no-go with mod_php5 for now... quite unstable and doesn't work...

BUT: the continuation of that work can be found under the name of eaccelerator. it works fine with mod_php 5.0.3:

if you want to see a running tiki on mod_php5 checkout

tiki-mobile seems to be strange on php5 cause of session restarting using transid and other weird stuff in