i just add '~amd64' on the KEYWORDS then add 'extensions = pdf.so' in /etc/php/cli-php4/php.ini and the html2pdf was able to produce pdf using pdflib
Deprecated ebuild, test/use dev-php{4,5}/pecl-pdflib and dev-lang/php. http://www.gentoo.org/proj/en/php/php-upgrading.xml