I just realized in testing, it appears worpress search is not matching my search term "php" with any post's tagged with "php" or in a category of "php" unless php is in the title or body, is that all the search searches for?
yes, WordPress search only searches title or post content. There are a few plugins that extend search to taxonomies, Relevanssi is one.
EDIT - The query WordPress produces for default search:
SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts WHERE 1=1 AND (((wp_posts.post_title LIKE '%test%') OR (wp_posts.post_content LIKE '%test%'))) AND wp_posts.post_type IN ('post', 'page', 'attachment') AND (wp_posts.post_status = 'publish' OR wp_posts.post_author = 1 AND wp_posts.post_status = 'private') ORDER BY wp_posts.post_date DESC LIMIT 0, 10