见 http://bbs.csdn.net/topics/390974677
$a = array(array(7,5),array(7,6,1),array(7,6,2,3,5),array(7,6,2,3,6));
$root = array();
foreach($a as $item) {
$p =& $root;
foreach($item as $k) {
if(!isset($p[$k])) $p[$k] = array();
$p =& $p[$k];
}
}
print_r($root);
