Sphider is a lightweight web spider and search engine written in PHP, using MySQL as its back end database. It is a great tool for adding search functionality to your web site or building your custom search engine. Sphider is small, easy to set up and modify, and is used in thousands of websites across the world.

PhpDig is a web spider and search engine written in PHP, using a MySQL database and flat file support. PhpDig builds a glossary with words found in indexed pages. On a search query, it displays a result page containing the search keys, ranked by occurrence.