there is a port called php52, and so . . .
sudo port install apache2
sudo port install php52 +apache2 +mysql5-server +pear +sqlite
sudo launchctl load -w /Library/LaunchDaemons/org.macports.apache2.plist
sudo port install phpmyadmin
and all the normal stuff that goes with it:
https://trac.macports.org/ticket/20410
http://2tbsp.com/content/install_apache_2_and_php_5_macports
http://trac.macports.org/wiki/howto/MAMP
http://bangpound.org/node/7548
http://drupal.org/node/360605
etc . . .