You will also need to tell PHP where to find PEAR.  A line like this is
required in your /usr/local/etc/php.ini:

        include_path = "/usr/local/share/pear"

If you do not already have it, you will need to compile GD support into PHP.
In general, this is done by cd lang/php4-extensions (if using PHP5, adjust
the path accordingly).  Run 'make config' to select GD support. Then run
'portupgrade -f php4-extensions' to compile the support.