Zebra_MPTT is a PHP class that provides an implementation of the modified preorder tree traversal algorithm making it easy for you to use MPTT in your PHP applications. It provides methods for adding nodes anywhere in the tree, deleting nodes, moving and copying nodes around the tree and methods for retrieving various information about the nodes. Zebra_MPTT uses table locks making sure that database integrity is always preserved and that concurrent MySQL sessions don't compromise data integrity. Also, Zebra_MPTT uses a caching mechanism which has as result the fact that regardless of the type, or the number of retrieval operations, the database is read only once per script execution.