Despite turning on errors in php.ini I wasn’t getting any error messages when I went to http://ipaddress/lists/ or http://ipaddress/lists/admin/, I just received a white screen of death. After adding error_log() statements thoughout the code to trackdown the issues I discovered that execution was getting as far as line 198 in /lists/admin/init.php
## remember the length of a hashed string $hash_length = strlen(hash(ENCRYPTION_ALGO,'some text'));
copying this to a test.php and running with a php test.php I received the error
Fatal error: Call to undefined function hash() in test.php.
Doing the following solved the issue
cd /usr/ports/security/php5-hash make install clean