The Public Knowledge Project’s OAI harvester is written in PHP 4:
“The PKP Open Archives Harvester is a free metadata indexing system developed by the Public Knowledge Project through its federally funded efforts to expand and improve access to research. The PKP OAI Harvester allows you to create a searchable index of the metadata from Open Archives Initiative-compliant archives, such as sites using Open Journal Systems or Open Conference Systems.” [1]
Sandro Groganz 