Tree-Shape algorithm

Algorithm,?
Test data
$ar = Array (
Array (id=>1,pid=>0),
Array (id=>2,pid=>0),
Array (id=>3,pid=>2),
Array (id=>4,pid=>0),
Array (id=>5,pid=>3),
Array (id=>6,pid=>1),
Array (id=>7,pid=>1),
Array (id=>8,pid=>6),
Array (id=>9,pid=>7),
Array (id=>10,pid=>9)
);

Sort functions
function cmd ($a, $b) {
if ($a [pid]== $b [PID]) return 0;
return $a [pid]> $b [pid]?1:-1;
}

Sort to avoid the presence of the parent node in the data after the child node, which occurs after multiple data modification
The purpose of sorting is to prevent the confusion caused by this situation
Uasort ($ar, CMD);

Define target array
$d = Array ();
Defines an array of indexes that is used to record the location of the node in the destination array
$ind = Array ();

foreach ($ar as $v) {
$v [Child] = array (); Attach a child item to each node
if ($v [pid] = = 0) {
$i = count ($d);
$d [$i] = $v;
$ind [$v [id]] =& $d [$i];
}else {
$i = count ($ind [$v [Pid]][child]);
$ind [$v [pid]][child][$i] = $v;
$ind [$v [id]] =& $ind [$v [pid]][child][$i];
}
}
Check Results
Print_r ($d);
?>

Algorithm features: Using the B + Tree concept, only one cycle can be used to generate a tree-shaped array