Tree is a smart array object inspired by the Node/Tree data structure and the UNIX file system's 'inodes'.
Tree is currently being rewritten to be non-recursive
The problem with tradition multi-dimensional arrays is that need multiple keys to access a nested element and sometimes you may not know now many layers deep you will have to go. This is not the case when dealing with directories in a system shell where you can use a single string to access an arbitrary depth. For example you can do this cd dir/other-dir which in an array would be like $arr['key']['other-key']. Trees can have access like this (more on this later):
$var = $tree[ ['key','other-key'] ];
// OR even better:
$var = $tree['key/other-key'];