PHP unlimited classification tree data formatting

Simplicity is the way to go....

function genTree($items,$id='id',$pid='pid',$son = 'children'){
 $tree = array(); //Formatted tree
 $tmpMap = array(); //Temporary flat data

 foreach ($items as $item) {
 $tmpMap[$item[$id]] = $item;
 }

 foreach ($items as $item) {
 if (isset($tmpMap[$item[$pid]])) {
 $tmpMap[$item[$pid]][$son][] = &$tmpMap[$item[$id]];
 } else {
 $tree[] = &$tmpMap[$item[$id]];
 }
 }
 unset($tmpMap);
 return $tree;
}

$items1 = array(
 array('id' = > 1, 'pid' => 0, 'name' => 'Level 11' ),
 array('id' => 11, 'pid' => 0, 'name' => 'Level 12' ),
 array('id' => 2, 'pid' => 1, 'name' => 'Level 21' ),
 array('id' => 10, 'pid' => 11, 'name' => 'Level 22' ),
 array('id' => 3, 'pid' => 1, 'name' => 'Level 23 ' ),
 array('id' => 12, 'pid' => 11, 'name' => 'Level 24' ),
 array('id' => 9, 'pid' = > 1, 'name' => 'Level 25' ),
 array('id' => 14, 'pid' => 1, 'name' => 'Level 26' ),
 array('id' => 4, 'pid' => 9, 'name' => 'Level 31' ),
 array('id' => 6, 'pid' => 9, 'name' => 'Level 3 32' ),
 array('id' => 7, 'pid' => 4, 'name' => 'Level 4 41' ),
 array('id ' => 8, 'pid' => 4, 'name' => 'Level 4 42' ),
 array('id' => 5, 'pid' => 4, 'name' = > 'Level 4 43' ),
 array('id' => 13, 'pid' => 4, 'name' => 'Level 4 44' ),
 array('id' => 15, 'pid' => 8, 'name' => 'Level 5 51' ),
 array('id' => 16, 'pid' => 8, 'name' => 'Five Level 52' ),
 array('id' => 17, 'pid' => 8, 'name' => 'Level 53' ),
 array('id' => 18, 'pid ' => 16, 'name' => 'Level 6 64' ),
);
var_dump(genTree($items1));