How PHP implements the infinite Classification (code simple) _php instance by the idea of passing the reference

Infinite level classification, mainly by storing the ID of the superior category and the classification path to realize

In my simpla, I used the infinite classification, using the PHP reference idea to achieve the infinite classification method, can be perfect to show such a classification pattern.

ID PID Name
1 04 Sichuan
2 0 Chongqing
3 10% are
4 1 Mianyang
5 3 High-tech Zone

The code looks like this:

The/**
  * array becomes an infinite class--the reference thought
  * @param array $items
  * @return Array */public
 static function Get_tree ($ Orig) {
  //resolve the subscript is not the beginning of the 1 problem
  $items = Array ();
  foreach ($orig as $key => $value) {
   $items [$value [' id ']] = $value;
  }
  Start assembly
  $tree = Array ();
  foreach ($items as $key => $item) {
   if ($item [' pid '] = = 0) {//is 0, 1-level classification
    $tree [] = & $items [$key];
   } else {
    if ($items [$item [' pid ']]) {//existence value is a level two classification
     $items [$item [' pid ']][' child '] = & $items [$key]; Reference direct assignment and change
    } else {//At least level three classification
     //Because it is a reference thought, there will be no value
     $tree [] = & $items [$key]
    ;
   }
  }} return $tree;
 }

The above content is very simple, if has the mistake or the better method, hoped can communicate with each other. Thank you.!