A printable version of the manual in pdf format is available from php.net. In indexer-conf you can assign specific TAGs to various sites and parts of a site. Metasymbols allow searching among groups of tags.
Categories are similar to tag feature, but nested.
So you can have one category inside another and so on. You have to use two characters for each level. Therefore a top- level category like 'Auto' would be 01. Zend Technologies Ltd. All rights reserved.